You can link red and blue in two ways: 1) Carry straight on along fireroad at top of final red descent and you end up at the bottom of the blue. Simple but a waste of height! 2) Better is to carry straight on but then follow signs for the black after half a mile or so and do a nice singletrack section of black (and maybe walk a couple of hard bits) and then the black joins the top of the blue. Then do the blue descent.
Either way you have a big climb back to the red after finishing the blue.
The red descent is better than the blue though, and it takes you back to where you started. So they’re best done separately IMO.
Green/blue in morning and then drive to red in afternoon, perhaps.
I agree Cwm Rhaedr is loads of fun. Short so do it 2-3 times, faster each time. Well, faster down, slower up probably!
@Hugor: Sunday was a nightmare!