Fantasy book with color-coded magic with gold magic as highest and enchanted armor

Question

I read this book back in high school (around 2001-2002) and for the life of me I can NOT remember it. I hope someone can help. The things I do remember are the following.

1. There was a system of magic in place that was color coded, with different colors for different things, with yellow magic being one of the first learned.
2. One of the characters was able to access a deeper level of magic, called gold, and was mentored to master it by another gold magic user. He also wasn't given a choice in the matter. These wielders of gold magic had a specific title but I don't remember what it was.
   • When wanting different effects, the colors were mentioned. You had to access that particular color of the magic spectrum to get the desired effect. Gold magic was an exception as it was a deeper level that could have aspects of all of them.
3. It also featured a tale of knights in enchanted armor.
4. These knights went through a portal to face some dark horror, I think some kind of vampire, and only one of them came back
5. The one that came back could not remove his armor until he encountered the one who had enchanted it, and so nearly choked to death of his beard
6. The older magician who enchanted the armor also enchanted other things, and to activate them you had to say his name. That way, if the item was stolen, no one except the people he had given it too, and therefore knew who he was, would be able to activate them.
7. At some point, one of the armors is worn by a female affected by the dark horror/vampire like state, and reflects her, beautiful on the outside but broken and ugly inside. It is subsequently broken
8. Near the end, the new wearers of the armor attempt to finish the quest of the originals, but I can't remember if they succeed or just set up a sequel, or even if there was a sequel.

Please help, if you can.

Answer 1

This might be David Gemmel's Knights of Dark Renown.

Once the legendary knights of the Gabala defended the nine duchies. Their hearts were beautiful; their armor was beyond compare. They were greater than princes, more than men.

But they were gone, disappeared through a demon-haunted gateway between worlds. Only one held back -- Manannan, whose every instinct told him to stay. Now he was the coward knight, and in torment.

Murder and black magic beset the land. Rumors circulated that the king was enchanted, changed, that his soul was dead . . . and that a reign of terror was about to begin.

Now Manannan realized he would have to face his darkest fears: he had no choice but to ride through that dreaded gate and seek out his vanished companions. And the secret he would learn there would tear his soul apart . . .

This Reddit thread mentions the beard situation:

Manannan in Gemmell's Knights of Dark Renown. Come close to choking to death from his enchanted helmet as his beard grew beneath the restrictive (and immovable) neck armour. It wasn't the original intent, but it ended up that way.

Searching in Google Books, gold magic is mentioned as part of the spectrum.

He closed his eyes, drawing the Yellow to him and feeling its warmth. His body lost all sensation of weight, and he seemed to be floating effortlessly in a wrm sea, slowly rolling over and over yet rising into the glow above. Often he had reached this stage, but mostly he remained a little below it, bathing in the Yellow. Tonight he rose and rose, seeking the Color of his life. The Yellow deepened into Gold, and his eyes snapped open to see that the sky was ablaze with color: Red, Green, White, Blue, Black, Violet — and Gold.

....

"... You walk the Gold, Lámfhada, and that is rare. It is special. All the Colors are subject to the Gold, and it is part of the great harmony that when the Colors are threatened, the Gold shines..."