A simple program that allows you to edit and save palettes for CC:Tweaked.

colsw.lua

--[[
MIT License

Copyright (c) 2023 simadude

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
]]
local filepath = ""

---@param fileHandler ReadHandle
local function applyPaletteFromFile(fileHandler)
    local cols = {}
    for i = 1, 16 do
        local line = fileHandler.readLine()
        if not line then
            error("File could not be read completely!")
        end
        local occurrences = {}
        for str in line:gmatch("%d+") do
            if not tonumber(str) then
                error(("Can't put %s as a number"):format(str))
            end
            occurrences[#occurrences+1] = tonumber(str)
        end
        if #occurrences > 3 then
            error("More colors than should be possible!")
        end
        cols[#cols+1] = {unpack(occurrences)}
    end
    for i = 1, 16 do
        term.setPaletteColor(2^(i-1), cols[i][1]/255, cols[i][2]/255, cols[i][3]/255)
    end
end

do
    local applyOnly = false
    if #arg > 2 then
        error("Too many arguments passed!")
    end
    for i, argument in ipairs(arg) do
        if argument == "--help" then
            print("Color Switch by Simadude")
            print("Version 1.0.0")
            print("A simple program that allows you to edit and save your palettes!\n")
            print("colsw apply [PATH]; applies the palette from the file and quits.\n")
            print("colsw [PATH]; opens existing palette file (or creates a new one)\n")
            print("colsw --help; prints out this helpful message\n")
            print("Repo - https://github.com/simadude/colorswitch")
            return
        elseif argument == "apply" and #arg == 2 and i == 1 then
            applyOnly = true
        elseif #arg == 1 and i == 1 then
            filepath = fs.combine(shell.dir(), argument)
            if fs.isDir(filepath) then
                error(("Path %s is not a file"):format(filepath))
            elseif fs.isReadOnly(filepath) then
                error(("Path %s is ReadOnly"):format(filepath))
            end
        elseif #arg == 2 and i == 2 and applyOnly then
            filepath = fs.combine(shell.dir(), argument)
            if fs.isDir(filepath) then
                error(("Path %s is not a file"):format(filepath))
            elseif fs.isReadOnly(filepath) then
                error(("Path %s is ReadOnly"):format(filepath))
            end
            if not fs.exists(filepath) then
                error(("Path %s does not exist"):format(filepath))
            end
        else
            error(("Encountered unforseen argument: %s"):format(argument))
        end
    end
    if filepath ~= "" and fs.exists(filepath) then
        local fh, e = fs.open(filepath, "r")
        if not fh then error(e) end
        ---@cast fh ReadHandle
        applyPaletteFromFile(fh);
    end
    if applyOnly then
        return
    end
end

-- index of a chosen color (1-16)
local chosenColor = 1
-- index of a chosen RGB value to change ( 1 - red, 2 - green, 3 - blue)
local chosenValue = 1

---@type string[]
local rgbstr = {};

local function saveFile()
    if filepath == "" then return end
    local fh, e = fs.open(filepath, "w")
    if not fh then error(e) end
    for i = 1, 16 do
        local r, g, b = term.getPaletteColor(2^(i-1))
        r, g, b = r*255, g*255, b*255
        fh.writeLine(("%s, %s, %s"):format(r, g, b))
    end
    fh.flush()
    fh.close()
end

local function changeRGB()
    ---@type number[]
    local rgb = {term.getPaletteColor(2^(chosenColor-1))}
    for i, value in ipairs(rgb) do
        rgbstr[i] = tostring(value*255)
    end
end

local function changePalette()
    local r, g, b = tonumber(rgbstr[1]) --[[@as number]], tonumber(rgbstr[2])--[[@as number]], tonumber(rgbstr[3])--[[@as number]]
    term.setPaletteColour(2^(chosenColor-1), r/255, g/255, b/255)
end

changeRGB()

local function colorToHex(col)
    return ("%x"):format(col)
end

local function redraw()
    term.clear()
    term.setCursorBlink(false)
    local width, height = term.getSize()
    local colorNames = {
        "white",
        "orange",
        "magenta",
        "lightBlue",
        "yellow",
        "lime",
        "pink",
        "gray",
        "lightGray",
        "cyan",
        "purple",
        "blue",
        "brown",
        "green",
        "red",
        "black"
    }
    local longestNameLength = 1;
    for _, colorName in ipairs(colorNames) do
        longestNameLength = math.max(longestNameLength, #colorName)
    end 
    for i = 1, 16 do
        local colorName = colorNames[i]
        term.setCursorPos(width - 8 - #colorName, i+1)
        term.blit(colorName..": ", ("0"):rep(#colorName+2), ("f"):rep(#colorName+1)..colorToHex(i-1))
        if chosenColor == i then
            term.setCursorPos(width - 8 - longestNameLength - 1, i+1)
            term.write((">"):rep(longestNameLength - #colorName + 1))
        end
        term.setCursorPos(width - 4 + ((i-1) % 4), height/2 + math.floor((i-1) / 4))
        term.blit(" ", "0", colorToHex(i-1))
    end

    term.setCursorPos(3, 5)
    term.write("red:   "..rgbstr[1])
    term.setCursorPos(3, 6)
    term.write("green: "..rgbstr[2])
    term.setCursorPos(3, 7)
    term.write("blue:  "..rgbstr[3])


    term.setCursorBlink(true)
    term.setCursorPos(10+#rgbstr[chosenValue], 4+chosenValue)
end

local holdingShift = false
local holdingCtrl = false

local function eventLoop()
    while true do
        local event = {os.pullEvent()}
        if event[1] == "char" then
            if tonumber(event[2]) then
                local digit = event[2]
                if tonumber(rgbstr[chosenValue]..digit) < 255 then
                    rgbstr[chosenValue] = tostring(tonumber(rgbstr[chosenValue]..digit))
                else
                    rgbstr[chosenValue] = "255"
                end
            elseif event[2] == "s" then
                changePalette()
                saveFile()
            elseif event[2] == "q" then
                return
            end
        elseif event[1] == "key" then
            if event[2] == keys.backspace then
                rgbstr[chosenValue] = tostring(tonumber(rgbstr[chosenValue]:sub(1, #rgbstr[chosenValue]-1)))
                if rgbstr[chosenValue] == "nil" then
                    rgbstr[chosenValue] = "0"
                end
            elseif event[2] == keys.down and not holdingShift then
                chosenValue = math.min(chosenValue + 1, 3)
            elseif event[2] == keys.up and not holdingShift then
                chosenValue = math.max(chosenValue - 1, 1)
            elseif event[2] == keys.down and holdingShift then
                chosenColor = math.min(chosenColor + 1, 16)
                changeRGB()
            elseif event[2] == keys.up and holdingShift then
                chosenColor = math.max(chosenColor - 1, 1)
                changeRGB()
            elseif event[2] == keys.leftShift then
                holdingShift = true
            end
        elseif event[1] == "key_up" then
            if event[2] == keys.leftShift then
                holdingShift = false
            end
        end
        redraw()
    end
end

term.clear()
redraw()
eventLoop()

term.clear()
term.setCursorPos(1, 1)