Thanks @spikeyxxx
I think I got the straight conversion working just dividing the 8-bit RGBby 255 and going into linear space. Not sure why Brecht was adding in the 0.5 but it was actually better results leaving it out. I now have a way to convert brush colors from any hex value I want in python for a brush color in blender. Pretty excited to figure out 1 piece of the puzzle.
Now I need to figure out the next piece of the puzzle converting the gamma correction on a hexidecimal value.
If anyone is interested in the code to do the color conversion I can post it later.
