Grab a free route map from the visitor center, you can link the black and red together. I find this this makes a more interesting ride, you swap the top end of the Red, which is pretty dull, for the best part of the Black.
Start on the Red from the visitor center, but pick up the black from the 'Jerry Noodle trail' (a fire road on the northern edge of the forest about half way around) its just before where Crosscliff car park is on the map.
Take the black where the low level North Shore starts, it starts on the right just before the bench and viewing point. From here the blacks quite interesting 'natural' riding, it will bring you back out at Dixons Hollow car park.
Between the start of the Red/Black in the car park, and the forst drive is another unmarked trail. It runs slightly uphill alongside the road. This comes out where the forest drive has a 90 degree turn and a little toll Booth, across the road is a fire road (not shown on map) go down this, turn right at the bottom and you'll be at Post 25 on the map to pick up the red again, last part of the reds the best IMO