Have you ever combined different yarns (by manufacturer name - bernat, redheart etc) in one blanket? I could be asking a dumb question, but I found a color by Bernat that Red Heart doesn't have, and I'd like to use them together with other Red Heart yarn (one blanket).
As long as the weight and fiber content of the yarns are the same, it shouldn't be a problem. Don't use all wool and all acrylic in the same blanket, or you will have a nightmare when laundering it.
i mix fibers and weights all the time. just use caution and keep in mind that you may have to change the size of your hook/needle to work up the same gauge and that laundering does become an issue. the only thing i don't do is mix handwash/machinewash fibers with dry clean only fibers.