I'm not aware of a code number from Lexus, although some others here may know more about it than I do. As you probably know, there were three RX300 interior colors: black, charcoal grey, and tan. I looked at the website you listed, and it looks to me like the 315 is what they match to the upholstery, the 03 for the trim, and the 133 (dark sandalwood) for the brown dash color. Hopefully, some others will chip in with their opinions, but that's how I interpret it. I'm glad to know about this site!