Where in Colorado are you looking at? There's a place fairly easy on the Arkansas between Salida and Cotapaxi on Hwy 50. I think it's called Point Bar?
38.470359, -105.871324
I've not been there, but it's public so you could try it.
Another public one is near Granite Co, called Cache Creek. I've been to that one and the road is very doable, but dirt and bumpy and very narrow. Lots of shiny mica there!
39.037268, -106.302093
There's a Pay to dig place just past Granite, CO, $10/person I've been to it and I've heard if you know where to dig there is gold there. We only got a few tiny fine pieces, but we're newbies and didn't pick the right spot obviously.
39.077160, -106.282178
The best thing to do is look for a local chapter of a mining organization like GPAA. GPOC (gold prospectors of colorado) is good as well, maybe better. Those organizations can tell you were to look locally.