I'm a 3-day user of ArtRage (discovered thanks to an enthusiastic friend of mine) and a 1-day member of the forum. Didn't have much time yet to browse all the topics, but it seems that there is some fantastic stuff everywhere.
The "one-hue" project, initially proposed by Andy, is the kind of challenging project that I find very appealing. I propose to constrain the rules even more, and see what kind of surprise could arise from you skillful guys. So here are the rules:
* Version 1: Start from a single layer canvas which contains a single bicolor gradient. The choice of the two limit colors, as well as the shape of the gradient is free, but only one gradient is allowed. Starting from that gradient, you only have the right to "smear" the existing paint with unloaded tools (brush, knife, or whatever) without adding any new paint. What can you paint with such a restricted rule?
* Version 2: Start from the same kind of single gradient picture but this time, you can use it as a tracing paper to automatically pickup the underlying color.
Version 2 offers much more flexibility as you can reorganize the colors much more easily. Version 1 is for the real smearing purists.
Here's an example of a Version1 painting obtained by a 5mn intensive smearing session in ArtRage. Unfortunately, the texture has suffered from the downscale to a 800x500 picture before uploading on the forum, but you got the general idea.
Hope you find the project interesting...