Use the greens to level up your crafting skill, buy special mats to make blue gear for yourself.
Slicing gives credits, rare patterns and opens paths in flashpoints (or so i hear, never tried flashpoints in beta).

And anyway, if you want to make money, just grab slicing and couple gathering professions and start selling mats.

I guess it's about what you value, utility, money making, self sufficiency (nobody can make everything on one toon anyway), just pick which brings you the most fun.