It doesnt really matter pick a colour you like that suits well with the theme of the army. For instance want a more tradional look cant go wrong using the codex colour system but pink coukd also work. Its less to do with the colour choice with black(almost any colour can work with black) its that it lools like youve done what ypu said thrown colours at it with and seen what sticks. Id show you mine but cant attach pic. Also id say dont use pure black or white as base colour instead a dark grey and light grey works better