Change material color and light color (light color more translucent)slightly on every trigger. I use this system at one of my games click for see
R G B
250 000 000
250 000 250
000 000 250
000 250 250
000 250 000
250 250 000
250 000 000
In my case i set it to start over in 100 steps. so :
250 * 6 = 1500
1500 / 100 = 15
R G B
250 200 200
250 200 250
200 200 250
200 250 250
200 250 200
250 250 200
250 200 200
50 * 6 = 300
300 / 100 = 3