Question (probably a dumb one) about Disney's "The Proud Family"

[Parco]

I saw this show for the first time ever a little while ago despite having heard about it for some time, and I just had one question about it that's probably going to sound really dumb to anyone who's a fan of the series, but I was just curious about this.

From what I could tell, nearly all of the characters on the show have realistic skin tones, so why are there a few whose skin tones are an odd-looking washed-out grayish/slight purplish color?

Like I said, probably a dumb question, but I was just curious.

[Uncle Beaglebub]

Yeah, I was wondering that too.

[Wolfcruiser]

I saw this show for the first time ever a little while ago despite having heard about it for some time, and I just had one question about it that's probably going to sound really dumb to anyone who's a fan of the series, but I was just curious about this.

From what I could tell, nearly all of the characters on the show have realistic skin tones, so why are there a few whose skin tones are an odd-looking washed-out grayish/slight purplish color?

Like I said, probably a dumb question, but I was just curious.
I'm guessing to show that it's okay to be another color or something, something similar. The same thing was done with Doug although there were many skin tones involved.

The Gross' Sisters tone works well for them :D