The Color Code attribute is on the Wireless Configuration page of the Installation Wizard in PTP 500/600/650/700.
The Color Code attribute is important in one particular application and completely pointless in every other application. In most applications, adjusting Color Code provides no benefit and does no harm, as long as the Tx setting at one end of the link matches the Rx setting at the other end of the link. In this case, it makes sense to leave Color Code on the default setting of A.
The exception to this straightforward and frankly boring advice is where two or more TDD synchronized links operate in close proximity and on the same channel. If this special case applies, or you're just curious, please read on.
PTP 650 constructs an estimate of the wireless transmission channel by measuring the phase and amplitude of fixed pilot tones. This is a standard technique in systems based on OFDM. PTP 650 minimises the impact of noise and interference on the channel estimate by averaging the phase and amplitude measurements of the pilot tones across a number of OFDM symbols. This is also a standard technique, and normally this averaging approach is sufficient to generate an accurate channel estimate.
The situation is different if the interference arises between PTP 650 links that are TDD synchronized and operated on the same channel. In this case, the interference is to some degree correlated with the wanted signal, since the frequency and TDD frame are identical in the two links. The averaging operation is not effective when the wanted signal and interference are correlated, and it is possible for the channel estimate to be degraded relative to a similar level of noise-like or uncorrelated interference. A less accurate channel estimate can result in lower sensitivity and lower availability of the more efficient modulation modes.
We address this problem by introducing five different phase shift patterns in the pilot tones, denoted as Color Code A to E. The phase-shift patterns have the effect of de-correlating the interference between the two links. We recommend setting different Color Codes wherever two synchronized PTP links are deployed on the same frequency, on opposite sides on the same tower, or where two or more links are deployed on the same channel in the same locality, such that one link might interfere with another. For all other cases, Color Code might as well be set to A.