Color picking is too subjective to be arbitrarily controlled by math. If you're working under very limiting restrictions then that may be hard to avoid, but generally you want your eye to determine what's wrong or right. Not a computer.
Staying conscious of color temperature is helpful. And how colors interact with each other, or "vibrate", when adjacent.
Do you decrease the rgb?
You mean saturation?
I always work in HSB. I can easily change just the saturation/chroma, hue/color, and lightness/value of my colors, and I do so constantly per what I'm trying to accomplish.
Post some examples for others to evaluate.