While we are on the subject of favourite liveries, what about your least favourite (i.e. worst) livery.
I had occasion to forsake my usual stamping ground last Thursday, and took a trip from Liverpool Street to Ipswich. I was utterly amazed that one of the privatized railway companies (viz. "one") has the utter brass nerve to put out several (I think they were 4-car) electric multiple units in an overall dirty dull grey colour, relieved only by the spindly lettering of the company's name in a sort of purple shade.
It looked totally hideous, and was IMNSHO an appalling advertisement for the company.