We're definitely aware that Legendary item drops can be difficult to see against certain textures, and that this can sometimes cause players to miss those drops completely.
While we'd like to avoid changing the actual color of the drops, we've been discussing a number of ways to make Legendary items on the ground more visible to the player. We've considered adding a new special sound, for example, having the location of the drop ping on the player's mini-map, and creating a unique FX effect that would appear underneath the item before it's picked up.
We haven't settled on any one solution yet, but the issue is certainly something we want to address and improve on. I'll make sure the additional options you listed get passed on to our design team so they can be considered as well.
