Hi all, picked my new second hand Specialised Epic, like wow, specially after stepping off an Orbea hardtail which served my purpose well. Anyway, went for a ride, Woodford to Glenbrook, during the descent my rear brake started making painful noises, didn't notice beforehand it now appears that my disc/rotor has blued, it's certainly a different colour to the front disc, checked pads, plenty of meat left, disc runs true. So how blue can they go before replacing, I assume softer pads would be available ? Any advice is good advice.