You are judging Spock’s room through human associations tastes. Remember, Vulcan blood is green and the planet Vulcan is red (Discovery even adds to this by showing red trees around Sarek’s property).
On Vulcan, red is the color of nature, so (assuming Vulcans even assign meaning to colors), red is likely a very calm and soothing color choice. Green is probably the Vulcan color of passion and/or danger.
From a Vulcan perspective, Spock’s room is a cozy cottage core with some historical knickknacks hung around.
Kirk’s green carpet, green plants, green lighting room is the Vulcan equivalent of a boudoir at best or blood-stained slaughterhouse at worst.