I'm not an artist, but I've been around UO long enough, and modding just enough, to get an idea of how some of it works.
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Some of the original CC art is a 2-D image, like a drawing on a piece of paper. If you recolor the whole image, like putting a piece of colored transparency over the drawing, it's pretty quick to do. This appears to be what we see most of the time for colorizations in UO. I'm not sure exactly how the CC works, but it's possible the base image is called and the color transparency called on the fly. This would mean you still only have 1 base art file, recolored on display. Either that, or the completely recolored image is saved as a new art file. If you recolored a candelabra into 5 shades, you'd have six files: the original, and a new file for each new color. Again, I'm not sure exactly how the CC is working, or if a mixture of recoloring on the fly and new art files is used.
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Other pieces of the original CC art were 3D models that were posed and pictures taken of the posed models. The pictures of the posed models are what we see in game. So, we are still seeing 2-D images, just pictures of models instead of drawings. Ralph Koster (UO's original lead designer) has spoken about this process in the comments of a former UO community member's
page, or on a blog she was running, which I currently can't find the link to. The community member you might know as Saphireena, from her pixel graphics challenge thread on Stratics.
If you're taking about a posed model you have to recolor it in each pose I believe, because you'd need to recolor each frame individually. So, if the candelabra was a posed model (i.e. could face east / west) that would be two separate files that would need to be recolored. If the CC is recoloring on the fly, that's still only two art files. If, however, the CC requires a new art file for each color, you'd be going from 6 files to 12 files. (1 base W, 5 colors W, 1 base E, 5 colors E).
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What you are asking about with regards to coloring the candelabra base separately from the candles, the UO team refers to as "partial hueing". At least they have in the past.
You can put the base candelabra in GIMP, or some other image editor, select out the part of the image you want and recolor it as you desire. However, you'd now have 2 images, one for the candles, and one for the base. The images have to be called and aligned in game properly, otherwise it would appear as though the candles were not attached to the base, or some other error. Since you'd now have 2 images, you'd now also have two files to keep track of and call properly. If the candelabra faced in two directions, you'd now have 4 files (candles W, base W, candles E, base E). If the partially hued candelabra was required to have individual art files for each color and faced in 1 direction, you'd have 7 files (candles W, base W, 5 colors W). If the partially hued candelabra was required to have individual art files for each color and faced in 2 directions, you'd have 14 files (candles W, base W, 5 colors W, candles E, base E, 5 colors E). Again, I don't know if the CC is coloring to display on the fly, or if it requires a separate art file for each color.
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If you're dealing with images that are static and only face in 1 or 2 directions, a few additional files don't seem to be that big of a deal. As items become more complex, face in more directions, or become animated, the number of art files scales logarithmically, into the 10s or 100s of files per item. Things get messy, fast.
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Finally, there is more than the technical aspect to why they don't partially hue items. There is the reaction to an art change. People who play the CC tend to be very particular about the art being exactly as it has been. The team has tried a couple times to partially hue items, only to receive extensive backlash from the CC community and revert out the partially hued art to the original form.
What you see as "looking better" others see as: a horrible change from that way the game has been for the last 27 years why on gods earth would you change it you stupid shmucks you are destroying the game what the hell is wrong with you you should all be fired immediately you are terrible people.
If only I was exaggerating.
