Question about The Muppet Show Intros

[tutter_fan]

My question is related to any given opening to The Muppet Show. I noticed that the background color of the arches was white throughout the beginning and middle of the theme but when the words "This is what we call The Muppet Show!!!" Each character has their arch going through different colors. I thought that it was a cool effect and I'm curious as to how it was done. Any info would be appreciated.