If the quilt is a total surprise I just try to observe surroundings to see what colors they like. For example my DMIL I made her quilt for Christmas that was to be a total complete surprise. I noticed she likes fall colors (lots of fall colors in the house) so a fall themed quilt was perfect. She absolutely loved it.
My DSD I told her outright I wanted to make her a quilt and asked her what colors and then I asked if she wanted to select a pattern and she left that up to me.
My DB has had input on the whole process. He told me colors then once I selected a design I ran it by him. When it came to the quilting he wanted to know if I could do his tattoos and I said sure just model for me so I can draw them.
For expectant mom's who got quilts from me I always asked what colors do you want.
So I guess the questions depend on how fussy the recipient is and how much of a surprise it is. Color preference has to rank #1 as the best question.