I hate, hate, hate them. They are far too intense and dominate the entire tree.
We spent an afternoon at the weekend trailing round garden centres looking for multi-coloured lights with NO blue. All in vain.
I hate them on houses as well and there is a house down the lane that has just blue lights everywhere, every year. I snarl every time we pass it.
Blue lights are just too pushy. I yearn for old-fashioned lanterns with old fashioned bulbs.