Think about this. PBSkids cartoons are much more educational than other kids cartoons that are out there. Would they be any more educational if they were in black and white instead of color?
PBS cartoon fare is, generally speaking, far different in terms of style and content that, say.... Cartoon Network original shows, or some on Nickelodeon.
More subdued colors, less jumpy action, etc. Compare Arthur to, say, Ren and Stimpy.
On the other hand, Katie KaBoom definitely counts as educational television for parents.
No, I don't think that cartoons are inherently useless. I've learned a lot from The Simpsons. I'm also pleased to note-- though perhaps I should feel some shame-- that the Schoolhouse Rock classic,
I'm Just a Bill got me an effortless A in high school American Government class, thank you very much.