Repeated measures using multispectral radiometry resolutely quantify canopy attributes of identical turfgrass cultivars under similar management. Concern regarding multispectral radiometric characterization of turfgrass canopies <24 h following synthetic phthalocyanine colorant application has been affirmed and is accordingly now avoided; yet explicit guidance on subsequent employ, at time(s) >24-h post-application, is lacking. Our objective assessed how petroleum-derived spray oil (PDSO) and synthetic Cu II phthalocyanine colorant (C) combination product influences creeping bentgrass (Agrostis stolonifera L.) reflectance up to 10 d following application. A maintained fairway received semi-monthly 9.76 kg ha^–1 soluble N treatments alone or in combination with 27 L PDSO+C ha^–1. Treatment by PDSO+C increased mean shoot growth (kg ha^–1) and dark green color index (DGCI) calculated by visible waveband reflectance. Yet reduced far red and near infrared reflectance from PDSO+C treated plots artificially deflated mean normalized differential vegetative indices (NDVI). Cautious interpretation of vegetative indices relying on 710- to 810-nm canopy reflectance is encouraged when evaluating fairways treated by PDSO and Cu II phthalocyanine combination product(s).