Proto-Indo-European *h₁reudh- "red, ruddy" became Proto-Germanic *rauđaz, becoming English red and Dutch rood. rood became Afrikaans rooi, found in rooibos, etymologically "red bush", a southern African plant.
*rauđaz became Old Norse rauðr, which combined with hvalr "whale" in Norwegian Nynorsk røyrkval. This was borrowed into French as rorqual, and then into English as the name for baleen whales, such as the humpback whale and mink whale. Why a whale would be called red is unclear. The OED suggests that they might have been called red because of the meat and because of a taboo on mentioning the whale's name at sea.
The suffixed zero-grade form *h₁rudh-ro- became Greek ἐρυθρός "red" and ἐρυθημα "redness of flush upon the skin", borrowed as erythema.