Line colors for crappie fishing really depend on what you're fishing, but if you're like me and you like fishing jigs for sensitivity, you're going to want to get a line that both lets you see and feel the action on the jig for you.
I used to use clear mono exclusively, until last fall. After fishing side-by-side with hi-vis users, and watching them catch 2 to my 1, I switched. I think I have caught more fish since switching.
Typically, I use Stren Hi-Vis gold in 4 lb test for casting. Mainly because it was cheap, and I couldn't find the Viscous when I was looking. I am about ready to get a spool of Hi-Vis Green Viscous from Monk's. The colors I've had the best luck with are yellows and golds, in hi-vis.
The action weight and other aspects of the line are going to depend on your specific rod, but I highly recommend hi-vis lines for crappie fishing.