I've created a few palettes/swatches in the past 12 months to help people with Painter, Artrage and Photoshop. Now it's time for me to look at the open source tool, GIMP.
Given that there is already an excellent COPIC palette (see [link]
), I'll add the Letraset "TRIA" markers to the resources available. (Yes, these colours are bright and saturated but they could be useful for some imitating markers. Keeping in mind the high saturation, I'd also recommend dropping the opacity if you really did want to go achieve a marker-like effect. Somewhere between 33% and 50% seems to work fine for me.)
To install, unzip the TRIA.zip file and place the TRIA.gpl in your palette folder. For example, under Windoze, look for your GIMP folder and then seek the palette subfolder. For example: C:\Documents and Settings\USER\.gimp-2.6\palettes
P.S. Corel Painter version is coming soon!