Here is an example of how you might use the ActionTimer plugin in combination with some Lua to change the "brightness" or "saturation" of a given color on a mouse over / mouse leave, using a "fade" effect.
; Set MetersToManage to the number of meters in the ActionTimer measure
; Set MouseOffColor to the RGB starting value
; Set BrightnessChange% to a positive or negative percentage of change
; Set ChangeSteps to the number of steps to take between MouseOff and MouseOver
; Set Wait to the number of milliseconds (no less than 1) between each change
; ChangeSteps and Wait will control the speed of the transition
[Variables]
MetersToManage=4
MouseOffColor=0,139,7
BrightnessChange%=-20
ChangeSteps=15
Wait=10
The Lua is reasonably "canned", and you shouldn't have to ever change it, just control things with those variables above in the skin.
; Set MetersToManage to the number of meters in the ActionTimer measure
; Set MouseOffColor to the RGB starting value
; Set SaturationChange% to a positive or negative percentage of change
; Set ChangeSteps to the number of steps to take between MouseOff and MouseOver
; Set Wait to the number of milliseconds (no less than 1) between each change
; ChangeSteps and Wait will control the speed of the transition
[Variables]
MetersToManage=4
MouseOffColor=99,8,0
SaturationChange%=-50
ChangeSteps=25
Wait=10