This is an interesting question. I know Vangelus has mentioned a few times on the TFW podcast that he much prefers cooler colours.

Apart from not being able to see my collection right now on account of it being in boxes, I don't think that would help much since I have a lot of characters of many different colours.

I tend to sometimes buy a mould based on colour though. I remember when the Darkmount/straxus mould cam out. I've never read the G1 comics so I had no attachment to the character. I liked the vehicle mode though, so decided to wait for a repaint (even though at that stage none had been announced). Later on the skullgrin version came out and I bought that because the colour of the toy made a lot more sense for the vehicle mode than a deep blue, even though blue is my favourite colour.

I bought the G2 MP Sideswipe based purely on the colour of the alt mode.

I like blues and reds in general but prefer a mix in my collection, otherwise the figures all start to blend together.