Markings on a bay...

[victorgrant]

Hi,

Buster has some markings I've not seen before... he has stripes on the back of his front legs and a dorsal stripe 🤔
Any idea why this is the case? Does it have a name? Should it be on his passport?
On a side note, can I change the company he is passported with if I wanted?
Will post pics in next comment as can't figure how to do it from here?
Please help.

I didn't find the right solution from the Internet.

References:
www.trotonline.co.uk/forum/showthread.php?58677-Markings-on-a-bay
Mobile Teaser Video

Thanks