If they haven't asked for help on improving their skills, then don't offer it. If you can't say something nice, say nothing at all. It may not look right to you, but it looks right to them and that is all that counts. It may not be your color choices, but it was theirs.
I like what I like and I don't particularly care about the rules on color choices or contrast. If I am making a gift for someone, then I care about what they like, even if it isn't my style.