The tree of my childhood, was a cornucopia of colours - there was no ryme or reason to the decor, it was every hand-made, 2nd run, or shiny new decoration my mom could use. Multicoloured blinking lights, and tinsel and garlands in every colour.
Sometime in my teens my mom decided to buy all new decorations, and decorate her tree in only red/gold.
When I got my own tree for the first time (in 2005) I bought a set of matching decorations, red, silver and white - and have been adding to that every year since.
However, last year, my roomate and I decided to have two trees. One real, for the living room, and I could set up my artificial tree (the red/white/silver one) in my bedroom. And we both agreed that it should be a Classic multi-coloured tree - so we bought pink, blue, green, purple, all sorts of ornaments and multicoloured lights, and went to down. It was great, and I loved it for being so sentimental.
I'll probably do the same thing this year.