I create a simple trigger to change the value of a variable. (vTab)
(sheet properties -> Trigger)
I changed the tab color on sheet properties -> General
-> tab settings -> Custom Colors
-> I created an if statement to apply the color according to the value of this variable.
I also created variables for the colors, so that you can set all of them in only on place.
Please, check attachment.
Hope it helps,
tab colors.qvw 127.5 K