The reason why is that you are trying to listen to a trunked system but are not programming a trunked system. You are treating the frequencies as conventional scanning and that does NOT work on a trunked system.
SF-FireRescue, I strongly urge you to read
Trunking Basics in the RR Wiki. What you are working with is trunked systems which is a far cry from the "old" frequency only days. Several departments nowadays share the same frequencies, but use Talk Groups (TGs) to differentiate between them.
The reason for the different colors is that Red denotes a Control Channel frequency on a trunked system and Blue is an alternate Control Channel. They have nothing to do with Police or Fire.
I strongly urge you to get some programming software to program your scanner as well as a programming cable. Get either
the 20-047 cable from RS, or
the 30-3290 cable from GRE. Also get some programming software.
You will find the software recommended here:
- WIN500 (My personal favorite)
- PSREdit500
- ARC Software by Butel
Each one of the programming software gives you a free 30-day trial period to try the software so you can choose the one best suited to your needs.
If you use WIN500 you will find
an illustrated tutorial here which gives you step-by-step help in programming your scanner.
EDIT TO ADD: If you will go to the
RR Database and click on your state, you will see "Trunked Systems] on the left of the page. The trick here is to know which system you are attempting to listen to. Click on that system and then scroll down. You will see a big section with frequencies. These frequencies are for the trunked system. The Control Channel frequencies (the ones in
RED) need to be programmed in. Scroll on down and find the TGs. The TGs need those frequencies in order for you hear them.
Again, I urge you to read "Trunking Basics" linked above so you will understand what is going on.