I agree with Onebyone. If the mother asked for red, white & blue, go for it! If she asked for peach & pink, do that instead regardless of whether you think those are appropriate colors for an infant boy.
Increasingly, I've seen a trend toward cool/cold colors over warm colors in nurseries but there are always those traditionalists that love pink for a girl's room or yellow as unisex and rebels who just love a pop of red or orange. I've definitely seen beautiful nurseries done in red, white & blue (as a nautical theme more than patriotic theme). In that case, keep in mind that a little red goes a long way. You could either go with a simple country quilt -- and maybe add just the tiniest amount of yellow along with the red, white & blue. Or you could go ultra modern with very little piecing & lots of open white areas to show off detailed quilting. Or anywhere in between. I love blue and white seersucker prints as well as tiny blender prints with little anchors on them in any of the 3 colors to carry out a nautical theme. And you can always tone it down a bit by adding some grey. There are so many adorable white-on-white prints for kids these days, you really can't go wrong. I'm working on a 1000 pyramids quilt that has white on white alphabet letters (capital & turned every which way) and it's so adorable and understated.
Just check with the mom first to see what she thinks (if you don't have a client/recipient in mind, I probably wouldn't risk a red-white-blue themed nursery quilt; very few people pick those colors for nurseries).