I love color - lots bright stuff especially! For me it depends on the horse. The ladies both look good in purple and teal so those are currently my favorites - we tried green and blue and that just wasn't working for them.
I don't own a horse, but I've stuck to a theme of navy blue and dark, conservative colours for my own gear! Amongst the jodhpurs that were a reasonable price (i.e. £20 rather than £60+), it was a choice between an ugly shade of fuscia, beige, or navy and blue - so I went for the last option. My mucker boots are also navy, and while I couldn't get navy half-chaps I did get black ones. My crop is navy too xD
WHEN I do own my own horse that'll depend on the gender and the coat color of the horse. I LOOOOOOOOVE pink, I have a lot of it in my own wardrobe, I also like light blue. I'm more of the pastel-y type person.