slack themes.txt

col_bg, menu_bg,act_bg, act_fg, hovr_bg,txt_fg,presence,mention[,top_bg, top_fg]

dark:
ayu dark:
#0A0E14,#01060E,#01060E,#3D424D,#01060E,#3D424D,#91B362,#E6B450
ayu mirage:
#1F2430,#191E2A,#191E2A,#707A8C,#191E2A,#707A8C,#A6CC70,#FFCC66
obsidian:
#293134,#2F393C,#293134,#93C763,#2F393C,#81969A,#EC7600,#EC7600
eva dark:
#21252B,#191E2A,#2C313A,#D7DAE0,#598DEF66,#B0B7C3,#98C379,#A78CFA,#282C34,#B0B7C3
mariana:
#303841,#3F4A55,#596673B3,#D8DEE9,#596673B3,#D8DEE9,#5C99D6,#EE932B
mariana (precomputed alpha):
#303841,#3F4A55,#4C5964,#D8DEE9,#4C5964,#D8DEE9,#5C99D6,#EE932B
mariana (color):
#303841,#3F4A55,#FAC761,#333333,#596673B3,#D8DEE9,#5C99D6,#5FB4B4
mariana (color, precomputed alpha):
#303841,#3F4A55,#FAC761,#333333,#4C5964,#D8DEE9,#5C99D6,#5FB4B4

light:
ayu light:
#FAFAFA,#FAFAFA,#959DA61A,#959DA6,#959DA61A,#959DA6,#99BF4D,#FF9940
ayu light (precomputed alpha):
#FAFAFA,#FAFAFA,#F0F1F2,#959DA6,#F0F1F2,#959DA6,#99BF4D,#FF9940
celeste:
#FFFFFF,#FFFFFF,#EEEEEE,#000000,#BBBBBB,#000000,#F58A3D,#FFDD33
celeste (color):
#FFFFFF,#FFFFFF,#FFDD33,#634D36,#BBBBBB,#000000,#F58A3D,#FF4D97
breakers:
#FCFDFD,#FCFDFD,#030303b3,#333333,#EBEEEF,#333333,#5C99D6,#EE932B
breakers (precomputed alpha):
#FCFDFD,#FCFDFD,#E3E5E8,#333333,#EBEEEF,#333333,#5C99D6,#EE932B
breakers (color):
#FCFDFD,#FCFDFD,#FAC761,#333333,#EBEEEF,#333333,#5C99D6,#5FB4B4

you can preview themes using https://slackthemes.net/
if theme contains alpha channel, slack will fail to apply pasted theme automatically, so some colors may have precomputed alpha blend