IMO there are intrinsically two designs of reels/spools - open free reels such as are mentioned above, and which you need for your application (I have several, and recommend one with a metal spool rather than plastic. Lots of good makes), and ratcheting or otherwise automatically locking ones for DSMB deployment. I generally carry both, the "ratcheting" one being the Buddy Reel. Any reel I've ever owned requires maintenance and usually some modification to work properly. The Buddy Reel in particular is prone to jamming after five or six deployments, but that is easily rectified with a bit of common sense and then the reel is totally reliable for many years. The open reel I'm currently using is by OMS and I like it, better than the DiveRite one I used before which fractured in my bag.
I recommend you do not try to use either reel for the other purpose, as it will be inconvenient and won't work properly.
The colour convention with DSMBs is red for a normal ascent and yellow for a diver emergency. This rule is universally applied in Europe and amongst serious tech divers in the US, but sadly US rec divers don't seem to have had it explained to them..... Best to affix a small slate to the top of your yellow bag so you can tell the people up top the nature of your emergency.