CC Madhya 20.330

śukla-rakta-kṛṣṇa-pīta — krame cāri varṇa
cāri varṇa dhari’ kṛṣṇa karena yuga-dharma
Word for word: 
śukla — white; rakta — red; kṛṣṇa — black; pīta — yellow; krame — one after another; cāri varṇa — four colors; cāri varṇa dhari’ — accepting these four colors; kṛṣṇa — Lord Kṛṣṇa; karena yuga-dharma — manifests His pastimes in different millenniums.
Translation: 
“In the four yugas — Satya, Tretā, Dvāpara and Kali — the Lord incarnates in four colors: white, red, black and yellow respectively. These are the colors of the incarnations in different millenniums.