Red is positive, black negative.
Classic Pioneer push terminals are side by side, not stacked like the ones with the locking tabs.
If you are talking about the speaker plugs, positive is -- (top horizontal tine).
Monaural and common ground stereo (if they ever used it) E is ground (negative) and there may be 4, 8 and 16 ohm taps, positive depending on the impedence of the speaker.