I don't know much about collocation either. I'd better talk about my usual collocation.
First of all, don't wear light-colored pants or jeans, because your legs are thick. This is my experience.
I usually like to wear dark jeans, and they are monochrome. Don't have anything with white or too many patterns on it, it should be elastic. If you can afford it, buy Lee's monochrome dark jeans. Not bad if you don't buy high imitation. I'm just 78 1 double or better 100, and it won't fade. Similar to sapphire blue, I still choose the black (but not pure black) pants I like to wear now. There is a vertical trouser line (decorative) from top to bottom in the middle to cover up my shortcomings and make my legs look thin. If you have a big ass, wear long clothes, preferably a small waist, to cover your hips and show your waist. If you have confidence in your upper body figure, you can wear anything.
Remember to wear dark pants.