On most Rinkers, the only lights that should be on when underway are the red/green and the white all-around on the mast. The transom light should be off when underway, so color doesn't matter.
@Grahamu if you have to back into your slip you may want to seriously see how much light you have at night. i replaced mine with a sealed LED light to just make it a bit easier to see at night getting back into my slip. Regardless to what you decide on. Make sure it is a fully sealed unit. That area gets pretty wet.
@davidbrooks you reminded me: the one I bought actually has two lights. For accent lighting, there's a low-intensity 4-color LED. For illumination when backing into the slip, there's a high-intensity white light.
Rule for stern and transom lights say that they are white. That said if you are under 40' you dont need the stern light to be legal. As long as you have the red/green bow lights and a white all around masthead light on the arch (360 degrees of light) you dont need a stern light. Either way though I would not change the transom light to blue.
Thank you all for the input, my transom light is not part of my navigation running light system. If I am moving my dinghy will be on the platform blocking the transom light. I have not used it much in the short time we have owned the boat but wanted to add some ambiance on those warm summer nights at anchor. I will check the lights mentioned in the posts above, thank you again.
Just an update, I discovered that the lens was removable and a festoon bulb fitted. I have now changed to a blue LED bulb. Also the spreader lights in the arch were the same Perko light so changed them too.
@LaRea They look brighter, difficult to tell with the shop lights on. Hoping to check them over the weekend with the lights off. Specs say 80 - 90 lumens.
Nice, our west marine started stocking those in two packs for around $10 to replace standard bulbs. A lot of fixtures use the same size. Certainly a nice upgrade from standard bulbs.
Answers
Go Steelers!!!
https://www.ebay.com/itm/Marine-Boat-Pontoon-LED-Prominence-VersiColor-RGB-RED-GREEN-BLUE-Docking-Light/232433151155