Disclosed are processes for application of dyes and topical chemistries to single yarns during a yarn rewind process. The process foregoes the need for downstream environmentally unfavorable dyeing and low PH chemical treatment processes on the finished carpet. Further, neutral pH dye solutions can be used instead of the prior art low pH dye solutions. The single, treated yarn can then be twisted, weaved and tufted, twisted yarn under dry conditions, and the twisted yarn subsequently weaved or weaved and tufted, into a finished fabric or carpet. Also disclosed are systems, BCF yarns, and carpets made from the BCF yarn treated by the disclosed processes.