I currently have neutral color gravel in 3 tanks; black in one.. EEK multi color in 2 10h & the 1g beta tank..
I enjoy neutral sand also, but I cant actually say I like any on best. I try to keep with the room & stand .. black stand & trim, black gravel... brown stand & trim neutral.. Kids rooms are more colorful, & the stones are too....
i use a large size gravel. it is made up of three or four dif colours. comes like this i didnt mix it myself. i like it beacuse it is small enough to not get clogged with poo, but big enough that the big turds big fish leave behind are inconspicuous. the colour also helps hide this.