The yellow-black-yellow is probably around 24 to 28 VCT. It goes to the regulators and also powers the preamp heaters with DC. The blue-blue is about 240VAC for the high Voltage. This is not center tapped so you'll need a full wave bridge to rectify it, just like the schematic. Red-red (unusual color choice) appears to be 6.3VAC for the power tube heaters. There should be enough current to power two EL34s or 6L6/5881s. I don't see anything to indicate what the PT primary might be. That might be confusing if there are multiple mains Voltage selections.