I don't have all the clues figured out, but I'm fairly sure the full name is...
Molybdenum has chemical symbol "Mo".
Moe's been on this Earth long enough to know the meaning of life.
Atomic number 42, reference to hitchhikers guide to the galaxy.
His clothing choice is a bit tacky; at our office parties, he always gets the lowest score. Maybe it's because he wears denim?
I suppose molybdenum is a tacky metal. Also it has "denum" in the name.
I heard he's started learning Japanese- to strengthen his aging mind, I guess.
Japanese sounds like Manganese.
He's been asking me to join him at his weekend classes. I've told him time and time again that I refuse, but as old-time partners he knows ruthless hounding will break through my iron will eventually.
"Iron will" is yet another reference to a metal.
As aforementioned, his taste in style is a bit lacking... he owns a old, dusty silver van that he drives to work
Molybdenum as a material looks old, dusty, and silver.
"Wallas Stevenfore" sounds similar to "Steven Wolfram". "Stanley Etun" sounds like a mixed up "Tungsten". The element is called Tungsten, although it is often called Wolfram.
Since the answer was almost completely found, here's the full walkthrough.
Molybdenum, or Moly B. Denum if you really want to make it a name. Atomic number 42, a movie reference as pointed out. His clothes are "TAcky", a reference to Tantalum, one of Mo's neighbors on the periodic table. TA has an atomic number of 73- a low score if you put it in the perspective of getting judged at a party! As mentioned, "denim" is a play on "denum".
Manga is a type of graphic novel from Japan, a reference to Manganese, another one of Mo's neighboring elements and a hint found above. Perhaps the most obscure wordplay was on "RUTHless hounding", which references Ruthenium, an element that is below Iron, the next obvious reference. The "silver VAN" describes Vanadium, the final neighbor mentioned in the original post.
The Third Hint:
The first two hints were found above. The third hint references "chroma", or color. It mentions that Mo cannot see "two dozen" colors- in other words, "24". Chromium has atomic number 24.
Therefore, the elements that were mentioned were: Vanadium, Chromium, Manganese, Technetium, Tungsten, Tantalum, (and Ruthenium & Iron). These elements are all neighbors of Molybdenum, but there are two neighbors that were never mentioned: Niobium and Rhenium, atomic numbers 41 and 75. Thus the passcode would be 4175 or 1457 depending on how you interpreted "Numbers in numerical order".