White lights are pretty and classic, but too much white is boring and too plain. It shows no color, in my opinion. Same thing when you paint a whole room white and have no color in it. It just doesn't look very interesting.
So I think that multicolored lights are more interesting and pretty.
Our tree has white lights, and the outdoor lights are colored. I like colored lights on a tree. That's what I grew up with, and it is what I love. Because we bought a prelit tree, we have white lights. We have a lot of red and gold ornaments and spun glass that pick up and reflect the light. I kinda think that white lights on some trees can be a little sterile looking.
I have several trees. Some are white lights. Some are multy colored. And our live one is small white globes and multy color mini lights to dazle it up.