Non-potable systems run reclaimed or recycled water that isn’t safe to drink, so code requires the lines be clearly marked. Purple (lavender) valve covers, caps, and tags identify reclaimed lines and keep them separate from the potable supply.
Use components rated and colored for reclaimed water on any zone fed by a non-potable source, and follow your local cross-connection rules. Where potable and non-potable systems meet, backflow protection is mandatory.