Female Hikers
Definitely power and safety in numbers. I hope you find some women to go with. Once you have a group, read through the other threads about good places to go so you're less likely to run into other hikers. There are some good suggestions in this group.
If you manage to put together a group that are strong hikers, maybe you should look into camping on longer trails. You should be able to get out further than most people go and then you'll be much more likely to run into people that aren't bothered by a group of naked female hikers.
Short of that, I recommend off piste, always being as gentle with nature as you can be. Find a national forest, hike out a while and then go off piste. As long as you've checked your maps (motor vehicle use maps are good to show you private vs. forest land) you should be able to get a good hike in without being bothered.
I'll second what LondoSun said. Being a strong advocate for getting out an hiking naked-in-nature I hope you find some women to hike with; I wish I could point you to some here in Colorado, but they seem few. Even my wife who has no problem being naked at a hot springs with other naked and clothed people doesn't have the naked hiking bug. She's done it, but usually leaves it to me. Consider renting a cabin or pitching a tent down at Valley View Hot Springs. It is a good safe place to do some moderate length, legal, naked hikes. There often a good number women that are down there who might hook up for a hike. Every time I have been down there, there have been a few women there by their self. VVHS also list "naturist hikes" as one of their activities they sponsor. Overall VVHS is a safe place to be naked.
What part of Colorado is your back yard. There are some safe places to go on the front range. Boulder is actually legal to go topless, so you can walk straight down Pearl Street topless if you want to. Not sure I'd recommend it though, if you're not yet comfortable with it. You might want to see if there's a "free the nipple" event wherever you are. I think those events tend to take place at the end of August, so there might be one this weekend where you are, or nearby.
Boulder Res is not a bad place to go topless either. Going topless is no problem there and I do see some people going topless from time to time. It was more prevalent a few years ago, but there have always been some people. If you're more comfortable with a friend, take someone. It's beautiful and relaxing. Your friend/s don't have to go topless if they're not comfortable. It's still a peaceful place.
You can wear even less there, if you so desire, but you need to be careful for that. Read the Boulder Res group posts about that.
If you're closer to Denver, you can try Mountain Air Ranch. Otherwise, National Forest is my recommendation. I always manage to find ways to be free. I'll let you know if I think of anything else.