Bruce didn’t have a favorite color until he was 28 and adopted Dick.
9 year old Grayson, as Boy Wonder, gripping Batman’s hand and skipping alongside him: Why is the Batmobile black? Is black your favorite color?
Bruce, thinking: It’s for stealth during the night.
Dick: So it has nothing to do with what colors you like?
Bruce, confused: I mean, I guess I like it in black just fine.
Dick: Is black your favorite color? My favorite colors are Red and green and yellow! Because those are the Robin colors! I also like blue, and purple, and pink…
Bruce, thinking about this question for the first time in his life: Hm. I think I’d say blue, too, chum. Now get into the car, please. Buckle up.
Dick, ecstatic: Blue! You should have a blue batsuit!
Years later, when Dick made his first suit as Nightwing, Bruce broke out the blue and grey batsuit that he hadn’t worn in years.