In case it helps anyone, I'm trying to avoid shades of brown with a random colour generator. Browns are hard to define a range for. It looks to me like the following covers all brown, though it may include a few slightly different hues too (like off coloured greens or purples), but you can tweak the limits: In terms of Hex codes for R,G,B: R < ee, R - 6 < G < R-3, B < G Eg: #993300 is brown. So if you want to avoid brown, then NOT this.

• Having R less then ee allows for inclusion of oranges and yellows.
• The most important thing is that G is a little less than R (if
  they're about the same or more you get yellows and greens), but not
  too much less than R (where you get reds).
• If B is larger than G, you get purples.

I need this for dots on a satellite map, which are hard to see if brown.