Hi there. Sorry if this is TMI, but I've been wondering about this for a long time and I cannot find the answers I need via Internet or books. I won't be rushing my Belle into the vet because of a bit of stain on her undercarriage. She seems to feel fine and be oblivious, but I'm worried about what it is...

Belle, who is spayed, has purplish brownish reddish stains on the area from where she wees. It's been there for a while. I was thinking that it was maybe her natural colouring, but now I'm worried it's not... I don't know. Recently, I thought I noticed the purplish stains on her mouth after she cleaned herself. Belle is a clean girl, she cleans herself every time after she goes, and for a long while at that! Is this why it has a strange colour? I would take a picture and post it but that would be obscene and Belle is a lady and wouldn't appreciate her undercarriage being on show like that... thanks very much for your time and hopefully I can get some answers and maybe I'm worrying for nothing.