I agree with Scotty. Keep it simple. A lot of hand signals are similar but with different meanings.
The ones I use most are pointing out hazards with either foot or hand, pointing at the gas tank when you need fuel, or food, or anything really... and the open/close hand gesture when someone leaves their indicator blinking behind you for miles and miles
Also, remember hand signals are for those behind you and hard to see if you're more than a few bikes back. Relay them to those behind you so they know what's up as well. It's almost impossible to tell someone in front of you something unless you stop or break formation. Unless it's really important, just deal with it 'til you stop.
There's bound to be a LOT of advice on riding in groups so I'll just add my 2 cents.
Remember that your safety is YOUR responsibility. Take that responsibility seriously and don't assume someone else has.
Most people think they're a skilled rider until they get into the back of a group. If the leader is going the speed limit the back of the pack can be doing 30mph over that at times to catch up. If that doesn't sound good to you, don't be anywhere near the back.
If you have any questions or concerns tell your ride captain right away, before you start riding with them. Get yourself moved to the front of the pack where you'll be more comfortable. It can make a huge difference in your enjoyment of the ride. If you do wind up in the back half make sure you know where the group is going for when you are inevitably separated from them.
Everything else is gravy after that.
Ride safe folks. Colorado is beautiful, you're gonna love it.