I'm out of town, teaching a workshop. No computer!
Please go to the posting from September 26th, 2013 on working with a limited palette. During our session in Volunteer Park there were several discussions about color mixing. A good place to begin focusing on making the colors you want is to start with only three colors: one each of red, yellow, and blue. Get as close to what you want as those three will allow, and trust that the result will be a cohesive image. Resist the temptation to add any additional colors!