My older son is almost nine years old and is really starting to want to dress himself. It’s easiest for me to ensure that he matches by buying clothes that pair together easily. To make life easier (and since sizes are consistent) I picked all items from J.Crew Crewcuts. I ordered some of this stuff for him but also threw in some extras for the mix + match aspect. Some of it he already had.
It’s almost fool proof. Except when he comes out of his room in the morning dressed head to toe in blue.