When was it decided that red and green sidelights would be used for navigation by sailing vessels?

In 1838 the US passed an act requiring a boat to have lights if traveling by night with no specific color. In 1846 the UK passed a law giving the Lord High Admiral power to determine the requirements for vessels. The Admiral determined in 1848 that a red and green light needed to be on a craft underway. While an anchored vessel also needed a white light. During the Washington Conference rules were adopted and became effective internationally in 1897.

https://en.wikipedia.org/wiki/Navigation_light