So I did look it up at Biblehub.
The word for rainbow, where rainbow appears is *iris*.
https://biblehub.com/greek/2463.htm
The word *toxon* is simply translated as *bow* with no clarification of whether it’s a rainbow or the weapon that shoots arrows. It is used only once in the NT and in that passage in Revelation 6 so there’s no clarification by comparing it to other passages.
https://biblehub.com/greek/5115.htm
Nevertheless, I still find it an interesting double meaning in English.
Yes, “Iris” in Greek is a real rainbow. The fake one is what the White Horseman Carries. The same term used in the Septuagint In Genesis 9