I'm coming out to the Denver area in a few months for a vacation.(I'm going to try and avoid Denver itself at all costs, but everything I need to do is pretty close in the area)

If I'm reading this right, I can open carry no problem pretty much anywhere other than in Denver county?

I'm not a resident in any of the 30 states that have a reciprocity agreement, so I have absolutely no chance of legal concealed carry?

Other than that and the 15 round magazine limit, it sounds like Colorado isn't all that bad for gun laws. Anything else I should watch out for?

While legal, I generally would recommend NOT open carry anywhere in the greater Denver counties (Boulder, Adams, Broomfield, Jeffco, Douglas, Arapahoe).  There's been a fair number of cases of open carry folks getting jacked up and hassled over the years.

Oh, yeah, I should clarify I have no intention of open carrying. But according to what I'm reading that's the only way for me to legally carry. I just want to be fairly knowledgeable of all applicable laws prior to getting there. I went to Wisconsin last year and found out after it was too late that hollow points were banned in the town I was in

It just seems so odd to me that there are legal avenues for residents of 30 ish states to legally conceal in CO, but since my state isn't on the list I have no legal way to conceal.

It seems like most of the laws are semi reasonable except for who exactly can carry is a mess. More likely than not... concealed is concealed.

Anything I should know about local fashion so as not to stick out like a soar thumb?

Yep

Depends solely on where you're going, what you're doing and season. I've been all over this state wearing boots, jeans and t-shirts or button ups with no issues. Outdoorsy clothing is everywhere and so is ranch wear. Seriously, you could wear Kuhl shorts with a Patagonia pullover, or Wranglers and pearl snaps and the locals wouldn't bat an eye