There is no use whatsoever in having a red bulb with a bearded dragon. They can see red light, so having it on at night will disturb their sleep. If you are having trouble keeping your night time temps over 70 degrees, you can use a ceramic heat emitter (CHE), they screw into a normal light socket but don't put out any light.
As for the Reptisun 5.0, I would say it's *probably* okay as long as you have an elevated basking spot, but when you upgrade to a larger viv (adult dragons need a 40 gallon minimum), you should upgrade to a 10.0 and try to get the fixture mounted inside the viv, so it's not filtered at all by the screen top.