As they said above build a bunch of them buy a few paints that look like what you could do, and do 3/5 test model of more if you need. Trust me, you futur self is going to love you for trying and testing the colors you want on it. Because there is nothing more disappointing and hobby killing than painting a squad, and looking at it with a feeling like you messed up and you don't like it.
So take the time to test
nécrons are really cool models so take your time.
Also, welcome to the forum