You say this has gone on for years. Maybe it's time to be more blunt.

Hub: gold icing looks like mustard.

You: hmm.. didn't see you running in to help. (get gold color just right).
or next year you can make the cake.

My dad has always treated my mom like this, they are 79yrs old now...
I swore from seeing this as a child I wouldn't let anyone do it to me.
My brother who is 4yrs younger is sort of opposite. Let his ex & current wife treat him similar to how dad treats mom.
Something of concern with your son having this as example of how to treat women when he gets of age & maybe even you later.

This is just my 2cents, no offense intended.

Take care of yourself.