Burgundy and mustard go really well. black, cobalt blue, purple, white
I think you can actually play with different colors, not just stick to neutrals because in my opinion the mustard is a neutral (dont ask me to explain why, it just seems like a neutral to me lol). you could always do the black, white, gray thing too
I instantly thought navy blue xD, anyway you can use any color really, choose one that matches your skin tone, if you have fair skin go for dark colors, if your skin is dark then go for light colors, I hope this helped :)
I like the bum on those pants. I'd like burgundy/red with those.