I have a red one too :)
I've seen glo-black used on a brown... word to the wise, don't. -shudder- it is NOT pretty! Glo-bay is the better choice for browns, even seal ones that look almost entirely black.
Some people don't believe the colour enhancing shampoos do anything, but IME they do. Glo-white will enhance anything, a little bit, but greys especially [or white markings]. I have two horses with 3 white socks each, and my formula for socks is to SCRUB with normal non-colour-enhancing shampoo, rinse, wash with glo-white making sure I get it down to the skin, rinse again, and then put a special powder on that gets any last stains out and keeps the socks clean until show day when you brush it on. It smells gross though... a bit like diluted bleach. You don't use much and you're supposed to mix it in water before you put it on.
I like Amino-Gloss for your normal non-colour-enhancing one. I tend to do the same thing minus the powder for the whole body of my bay-brown. I don't think I've ever actually scrubbed my chestnut up as if I were going to a show - haven't shown her yet so all the show prep we've done is purely for practice but years ago I had a little white-grey Welshie with a few chestnut fleabites and he was just washed in glo-white for shows because he was pretty much white all over. It darkened and reddened his fleabites SO much.
I would try the glo-chestnut, making sure not to let it get on his socks until the rinsing stage [and then only because it'll only be on for a second!], for his whole body, for this show. Then try the glo-white all over at some later stage, and see which result you like best and if there's any difference :)