I've been wondering this basically since we found out he'd been training for the Blackguard too. I expect an extremely dramatic reveal at some stage in Blood Mirror, that's the only reason I can think of for Weeks to leave things so mysterious. We might be able to gain some sort of hint by examining his personality. He definitely seems far more on the rational side than the emotional to me, and is extremely unsympathetic towards others. He also has excellent self-control. I'd lean towards yellow, blue, or superviolet out of the colours we know the metaphysical effects of. I think if he could draft superviolet he'd most likely have used it to navigate the darkness of Andross's room, and if not Gavin would have commented on him not even needing it to navigate in the darkness. Which leaves, yellow, blue, chi, or paryl. He's related to Tremblefist and Ironfist, who are both Blues I think (Ironfist definitely is, have we seen Tremblefist draft?)
Thoughts: If he was training for the Blackguard he's nearly definitely a monochrome. Except as head of the Broken Eye he's going to have a lot of secrets, and more colours could be one of them, so maybe that's not all that helpful.
Kip at one point asks himself if he can draft faster than both Andross and Grinwoody, so I would assume so.
In The Blinding Knife when Kip is talking to Ironfist after Janus Borig, they discuss that Grinwoody went through the Blackguard training. Ironfist stated that Grinwoody was 'barely even a drafter'
They don't mention what color/s though.
That's a great catch! But we also need to remember that Ironfist has a good reason to lie about Grinwoody's abilities. It's possible that he has subchromat drafting abilities that Ironfist doesn't want to reveal.
I'm rereading Blinding Knife right now and just got past that part like yesterday! Earlier in my rereading I noticed someone explicitly say that Grinwoody wasn't a drafter, which creates a weird contradiction. Guess it's either a case of a mistaken POV character, Weeks deciding to retcon it, or it just being a mistake/continuity error. Definitely more inclined to go with the "barely a drafter" as true.
Do you happen to remember where you read someone stating he couldn't draft?
Not exactly. Pretty sure it was when Gavin was summoned to Andross's room in BP.
Found it. Chapter 47 (p307) of BP. From Gavin's POV: "Neither Grinwoody nor Andross was a superviolet, so Gavin could have as much of the eerie violet light as he wanted... He [Grinwoody] wasn't a drafter, so he couldn't directly control his eyes."
Whenever Either Gavin or Kip is in the room with Andross, Grinwoody is wearing the nightvision goggles, or he's holding a superviolet torch. It doesn't mention the goggles during some interactions, but (I think) during the first time or second time kip goes to play nine kings with Andross, it gets mentioned that Grinwoody is wearing strange goggles.
As far as his drafting ability goes, I suppose that doesn't explain much, but unless he's super sneaky I think that might rule out the possibility that he's a superviolet drafter. He could be a paryl drafter. As stated, it's mentioned that he can "barely" draft. The same things are said about Teia. That paryl isn't a "real" color. Considering paryls are also more likely to be subchromats, that could also explain it.
As far as "real" colors go, it seems the most likely that he could be a blue. As Kelvinator said, he IS related to ironfist, who's a blue, so that makes that at least somewhat likely. But unless we got more information on the rest of the drafters in Ironfist's line, it seems like just a guess.
It'd be easier to make a good guess if the genetics of drafting were more predictable/simple =S We know that someone who has drafters in their ancestry is more likely to draft, and presumably more likely to draft similar parts of the spectrum (otherwise why seek out bichromes/polychromes or seek out partners from different parts of the spectrum), or at least that most of the noble houses believe this is so, though they don't really seem to have that much evidence for this belief (although the prevalence of drafters among the noble houses implies at least some level of hereditaryness, and I mean it just makes sense that they would be).
I forgot about the glasses, that's a good pick up. That probably rules out both paryl and subred, because then he wouldn't need them.
So we've probably got Blue(likely)/Green(unlikely)/Yellow(plausible)Orange/(plausible)Red(unlikely)/Chi(unlikely just on probability of any given person being a Chi drafter, more likely because this is a story and secrets and stuff so it kinda fits), where likely=we have some sort of reason to indicate this colour, unlikely is just me arbitrarily deciding it doesn't fit with his character, plausible for one that fits his character but we don't have any evidence either way for).
Hmmm. He's certainly very slippery, perhaps he could be an Orange? (kinda really hoping he's not because according to the quiz that's my colour, and also I've quite liked the Oranges we've seen so far for the most part).
I think grinwoody is a paryl drafter only. I agree, Ironfist has an excellent reason to lie. Never saw that one coming! Lol. The reason i believe this has to do with the goggles he wears in the first 2 books, his seemingly perfect knowledge of the layout of the rooms Andross owns, etc. The by far easiest explanation is that he drafts paryl, not that he has memorized room layouts. And he seems to be able to help Andross cheat at nine kings, so he likely can see in the dark somehow.
If Grinwoody could draft chi, he would've been there at Teia's testing, and they'd have been able to test her for chi, but as they said, there were no chi drafters present.