When, due to a lack of extra females, one female purchases a set of different color lipstick and proceeds to give a male driver a blowjob, applying a new color every few minutes until the driver's penis looks like a gay pride flag.
"Hey honey, why don't you pick up four extra colors of lipstick while you're in CVS, and then you can give me a road rainbow on the way to church."
A peach rainbow is the new term for white people who argue especially on the Internet with POC (people of color) about who is truly racist and whether or not they think all white people are racist. They are so fragile they think people of color are hurting them by pointing out racism. They think they know more about racism than POC and will argue to no end with POC about how it's racist of POC to point out and call out racism.
Complete the rainbow is the action of having sexual intercourse with one or more individuals from each of the fraternities on campus. Leaving this way, an entire variety of fraternity colors, like a rainbow.
Claire decided to Complete the Rainbow, thus, slept with guys from each of the fraternities on her school.