When you put a 2* saddle cloth, leg wraps and ear bonnet of the same base colour on a horse, they also get an extra bonus called the colour bonus. You can see it on the horse's bonus tab. The pieces of tack just need to have one common colour, so for instance, a blue and green saddle cloth, green leg wraps and a green and white ear bonnet will work just as well as a blue saddle cloth, blue leg wraps and a white and blue ear bonnet.

Thank you. That makes sense I just didn't know about it