Overrides for things marked in green (high priority) and yellow (low priority): http://i.imgur.com/I03IVKt.png
for the play/pause icons is it just the colours (prefered) or the entire image?
Entire image, but it's probably the less important one, so it can wait for a future release.
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About the headers/columns colors... well, it's not really needed right now, but I think it makes a lot of sense:
- Unifies each column/panel color (looks better)
- You could assign, for example, alternating rows only to the main panel (it's the only place where they're functionally needed), so the playing tracks element could be in a narrow side panel without alt. rows but have them when you move it to the main panel. Right now you have to choose a specific look for it, whatever the panel it's going to be in.
- If a skin has 4 different colored side columns/panels and the user is only going to use 1 or 2 of them, they can choose between different colored panels to put their elements.
- Simplifies the skin making process (right now all the different settings mixed between elements and panels it's a bit of a mess - but they could work as overrides, if anyone wants to use them)
The cons are obvious, it's a lot of work for you to change all that right now. Maybe you should leave it for a future version.