In especially older animated films/series, parts that move or will move in a scene tend to be a somewhat brighter colour than whatever stationary thing they’re attached to. What aspect of the animation process was responsible for this? I vaguely recall that the moving bits were on different ‘cells’ or something, but if that’s true, why couldn’t they be the same colour regardless?
The backgrounds were often done by different artists on one cel, and the moving parts were on a different cel.
Since the work is being done by different people on different pieces of acetate, it’s not surprising that they’d be working out of different paints and inks. Another reason the moving bits can look different is that they’re at the top of the stack of cels, so they’re being seen and photographed directly. The underlying cels are being photographed through the other cels, so if the upper cels are anything less than perfectly clear, they’ll be a bit diffused.
It was normal for cels to be washed off and re-used, since so many were needed. It’s not at all unlikely that they’d start to get a bit hazy with traces of paint not cleaned off, or simply scuffed up from all the handling.
I just wanted to stop by and add that this was particularly noticeable in Scooby Doo. I can’t tell you how many times they’d be looking for a ghost, and would walk back and forth by a bookcase with ONE glaringly-bright red book! Hidden passage, anyone?
Plus the cels are stacked and the light is reflected and refracted as it passes through each layer and the gap between. The top cel is the clearest with the truest colors and the bottom cel is the worst.
That bugs me, too. They told us at Sheridan that, properly, there ought to be different tints of the character colours, so that as a particular character rose towards the surface in the stack of cels, it was painted lighter and lighter, and looked the same when filmed. Bit I don’t know whether many people did that. It would multiply the work enormously, and reduce the ability to swap artwork across layers.
Another part of the noticeability is that the animated parts in classical animation are usually much simpler than the backgrounds.
If you look at a stack of cells in real life, the deeper ones will indeed be murkier toned. For being transparent, they still aren’t air. And the bits that are more likely to move are generally going to be higher in the stack, if only for easy of swapping.
I was going to say Bullwinkle. Watch Bullwinkle talking, especially in close-up, and you can’t help but notice that his jaw is a completely different shade of brown from the rest of him.
Which falls under what Sunspace and I said. At the time, and this is hard to admit because the animation world in 1960 was FILLED with shops taking every shortcut, Jay Ward found even more shortcuts to take. (sigh) The money, what little there was, went into the scripts and voice talent. The animation put it on TV, where Jay made more money than with radio.
That was a different issue, caused by a completely different paint, and a different painting style, used for backgrounds.
In fact, even now backgrounds are painted differently to foreground cels, but in digital it’s easier to blend them, and colour-grade, so it’s not so jarring.