Here is a song that includes both, "I Can Sing a Rainbow"
Only one problem with the accuracy of this song is that the colour pink is not in a rainbow.
I Can Sing a Rainbow
Red and yellow and pink and green
Purple and orange and blue.
I can sing a rainbow, sing a rainbow,
sing a rainbow too.
Listen with your eyes
Listen with your ears
And sing everything you see
I can sing a rainbow, sing a rainbow
sing along with me.
Red and yellow and pink and green
Purple and orange and blue.
I can sing a rainbow, sing a rainbow,
sing a rainbow too.
Note: I'm not a singer but do the best I can.
If you would like to hear a better version of the song you can find it here.