Possibly you prefer contrasting colour schemes than complimentary colour schemes. Blue and orange are opposite each other on a colour wheel, while blue and green sit next to each other. In theory they both work but for different reasons.
Actually come to think of it, I think you're right. I've never thought about it before.
I loved the old SPT and GMPTE orange and brown/black liveries, quite a contrast there. I also liked BR Blue Grey.
Although maybe there are some complimentary liveries I do like. My favourite livery of all is the old Provincial Sector light blue on the 143s, absolutely gorgeous.