Who's idea was it to make him gold, then red and yellow? Stan? Jack? Heck?

In the rest of comics, an "iron man" usually meant a grey character.

I ask because he seems to be the one metal guy that made it big (and I'm guessing in part because he isn't the grey or monotone robot-looking armored/robot man that we had in the Golden Age). I wonder if the 90's Steel had a better looking, more colorful look, if it would've helped. The previous Steel looked too much like a Captain America clone. I think that kept him from being too interesting.

Steve Ditko designed it.

If you look at all the designs Steve Ditko did (Spider-man, Doctor Strange, Blue Beetle, Creeper, Hawk and DOve, etc.) it's no surprise that his first thing on Iron Man was to jazz it up with some color.

If you look at this series of Ditko panels (the first time the red and yellow were drawn), he gives an elaborate explanation of how the pieces fit together, but nothing he says seems to track with why some parts are yellow, and some are red.

Ditko seemed to have a thing for these sequences where the character takes us through his costume design.

Ditko didn't show him putting on the metal undies.

Before the Ditko Red and Gold Armor redesign, though, Stark changed his
armor from gray to all gold in Tales of Suspense 40. Some socialite or
another (can't recall her name) told Tony that the gray Iron Man was awful
looking, and that she thought he should be a knight in golden armor (or
something like that).

The armor also got some other improvements (collapsible components so
that it could be "briefcased").

The color change was likely made for the same reason that the Hulk was
made green. Gray was hard to make look consistent in the comic, so
gray characters did not look the same from page to page.

That costume building segment of the Creeper's origin has always stuck in my mind. Jack grabbing random items and talking his way through it.

When Captain Atom changed from his old gold and red outfit/containment suit,
to his new spray-on metal suit, Ditko also had Adam describing the process,
the spray on "atomic" symbol, and his hair color switch, etc.

I also seem to recall various Spider-Man villains, like the Vulture, helpfully
explaining his suit's capabilities (to the reader) when we first encounter him.
Seems a common Ditko story-telling mechanic.

Doesn't everyone give a verbal play-by-play as they get dressed in the morning?

"I'll wear this black belt. It will go with my black shoes that I plan on wearing."

Yes.

JB needs to do a series that fills in the missing panels that have the Ditko characters picking out their underwear.

Ditko designed the first yellow and red armour. The gold version that preceded it was just recoloured from the original grey (iron) look, with the same tin can design (which I think was Kirby's). I don't know why Stan changed it, but I'd guess it was some combination of the reason he changed The Hulk from grey — it looked dull and indistinct in print — and the reasoning he wrote into the story itself, that the grey armour made Iron Man look scary rather than heroic.

I thought that was just me....

And he IS grey--but he's kind of vain, so he uses that "Just for Men" stuff to cover it up.

Grecian Formula?

Finally, some answers!

I recall reading this as a kid...really cool.

:sob: Linda has me foed.

Yes.
This (#48) was the third Tales of Suspense comic that Dad owned.
He also had #46 (vs the Crimson Dynamo) and #47 (vs the Melter), which both
featured Iron Man in the all golden armor. The Melter issue always bothered me
because I knew as a kid how hot metal had to be to melt, and here, the melted
metal was poring over Stark's arm without a cry out of him. I concluded that the
Melter's ray must have been doing something other than melting.

Wish I had gone back and bought the 45 issues before Dad's first, though.
I should have done that decades ago. I did buy quite a few of the issues
that he missed after #49, though.

I probably should have picked up that Iron man Omnibus when it came out.
Why the hell do books like that need to go OOP and command collector's
pricing later on? That just seems nuts to me. They should periodically
print a bunch of those and keep them in stock.