Yes Gareth, it is a true yellow, and as Bernard has already said, not the jade at all. It's quite an acidic kind of yellow, similar to yellow pearline, as Bernard noted, though to me it is not as warm a shade. Just a hint more tangy.
It's the only example I have ever seen, and I can't actually recall when we bought it now (maybe 10 or 15 years back). My parents have a small collection of vaseline and pearline and we gave it to them to include in the display. I just happened to notice it today...silly of me really to have "forgotten" about something so lovely. We'll try and get a pic of it tomorrow.