I don't think you can recolor DX plugin objects (such as meters, etc) You'd have to do it manually.
This is really impossible
This is correct in that this is not possible to do directly. However, it's relatively straight forward.
1. Create an image for your bar (e.g. colour block /gradient 100x20 pixels)
2. Create a text object to store the meter value
3. Create your meter and use the "Set text of object" option - pointing it to the text object you created
4. Add a simple script to the text object on a timer that (optionally) matches the interval of the meter update and sets the width of the bar you created in (1) based on the text value e.g.
DesktopX.Object("cpu").Width = Object.Text
5. Hide the Text object(2) and meter object(3)
6. Recolour your bar object
Appreciate it's OT, but it may allow up to focus on getting a plugin that works with UAC rather than worrying about the colour