example of outline text and sprites, and also palette swapping...

outline.p8

pico-8 cartridge // http://www.pico-8.com
version 16
__lua__
function _init()
 _t=0
 sprites={1,2,3,4}
end

function _update()
 _t+=1
end

function _draw()
 cls(1)
 outline("hello",64,48,12,8)
 outline({sprites[flr(_t/8)%#sprites+1],6},64,64,10,8)
 outline({sprites[flr(_t/8)%#sprites+1],6},72,72)
 outline({sprites[flr(_t/8)%#sprites+1],6},80,80,12)
end

-- takes:
-- what = string | object
-- if it's an object:
-- {sprite_index, base_color}
function outline(what,x,y,f,b)
 local f = f or 7 -- white
 local b = b or 0 -- black
 if type(what) == "string" then
  -- string outline
  for i=-1,1 do
   for j=-1,1 do
    print(what,x+i,y+j,b)
   end
  end
  print(what,x,y,f)
 else
  -- sprite outline
  pal(what[2],b)
  for i=-1,1 do
   for j=-1,1 do
    spr(what[1],x+i,y+j) 
   end
  end
  pal(what[2],f)
  spr(what[1],x,y)
  pal()
 end
end
__gfx__
00000000000000000006060000000000000606000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000606000066660000060600006666000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00700700006666000006066600666600000606660000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00077000000606660006666600060666000666660000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00077000060666660060000000066666060000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00700700660000000660660006600000660666000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000660666060660660006606600660666060000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000006006000006600000600600000660000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000