I use Nu-Image on my guy, he's a black and white overo, so we have a lot of black.
I use nu-image suppliment(it makes them grow out a new blacker shinyer coat, and shed the old dull, bleached one. I get TONS of compliments on his color and shinyness everyday.
I think I have some before and after shots... hmm...
After= ( this is one tub of nu-image later) Just over a month.
This one shows off his shinyness in the sun
And this one shows off his over-all black color without the sun on him( and his better jumping position... lol)
Its an expensive suppliment, but it REALLY works, fast, and amazingly.
You can also look into getting a uv fly mask, sheet, and tail bags.
Good Luck, and another note, the shampoos/conditioners with color deposit (like aveda)will temporarly re-blacken the orange. So I would only do it the week going up to a show or something.