Here are what I've seen for Watson 540's: I've never seen them in yellow. That doesn't mean they don't exist, I just haven't seen any.
I'll tell ya Spens93, after searching for the yellows and coming up basically empty handed, certainly doesn't mean they don't exist, but taking something you cant identify via internet, should raise first red flag. The pill itself is either fake or was riding in someone's pocket for a while if it's real, we've all probably pulled a pill out of our pockets looking like that. stay safe brother....!
Wish I could have commented on this thread sooner. Its either fake or like Bottlefed said very worn. Did you take it? If you cannot ID it online (I have even been able to ID specific street MDMA pills just using google) than I would probably put it in my 2nd stash box- the "Im not sure if this is a good idea to take but I want to save it anyway" box. Or flush it.