You question "is your set up (open sights) good for hunting purposes?" is easy to answer. Yes they are. Over the last 12 years I have been hunting mostly with muzzleloaders. Now most of the game my son and I have killed with them were with our Hawkens and Renegades. But the sights are the same as my inlines.
In real low light the front sight can be hard to see. But in my experience in low light I center the spot I want to hit in the globe sight, and peep sight. I would say I guess I shoot more instinctive in low light but I am also talking very close range.
Where these sights really shine is in good light. You can use your range finder and get the range. Set the sight for the shot and hold dead on. No hold over, no hold under. DEAD ON.
I like the Lee Shavers medium pin insert. My son like the more traditional cross hair. I like mine with a little white paint on it, he doesn't.
We have killed a PILE of Deer, Antelope, and a few elk.
Are peep sights perfect? No they are not, but in my opinion they are 1000 times better than a regular iron sight. I set my sights for 100 yards when I am hunting. If the shot is under that and it is a quick shot I do hold low and get it done. In my experience if the shot is over 100 yards I am able to get a range and set my sight.
Lets say for instance I was antelope hunting. I shot my antelope at 89 yards but because of the angle of the shot He was kneeling down facing me at the water hole. The buck went down but got right back up. My bullet hit the spine and deflected down the back not going into the lungs. I quickly reloaded and set the sight for 150. When the buck got to 150 yards, I used a cow elk call and he stopped for just a moment. The next one was centered through the neck.
I never take a first shot at an animal past 150 yards. But I am sighted in out to 300 if something happens and I have to clean up a mess. So far I haven't had to shoot past 150 yards with my bullets.
Your next question is "would your sight set up work for me while hunting elk in colorado?"
Well that one is a little harder to say since I have never hunted there. But I have hunted deer, elk, and antelope a lot. I have been in a lot of Idaho's mountains. My sights have never let me down. Here are a few of the animals we have killed using adjustable peep sights and Lee Shavers inserts.