We've always used white. DH prefers white, & I've always thought white looked elegant & warm & inviting.
However, last Christmas we bought a new tree for our family room which has the option for both white and multi-colored. The kids loved the multi-colored lights! And, although, we can go back & forth between the white & the multi, we were leaving the lights on the multi more often. So much so, that I changed the garland on our mantel from white lights to multi-colored lights so that the garland would match. LOL! (And I never thought we'd ever have multi-colored lights!) It's just a fun & festive look for our family room.
The lights on our kitchen tree & living room tree are white.