Q.Do some Hibiscus change to a totally different color after years?
We have a hibiscus that has had all peach color flowers on it for 10-20 years. NO graphing!! Two weeks ago it got one brilliant red flower along with the peach on the same set of blossoms. Now it has another red one but not even from the same main branch as the first. Help me out,evolution?
Will try sending a photo.

Yes, it is entirely possible!
This link will help you understand the causes.
http://www.hiddenvalleyhibiscus.com/misc/colors.htm