Orange stains on my westie's coat Grooming

My Lily, who is 7, has always had a brilliant white coat. See her pic on my profile as example. I moved last August 2019. Shortly after she began to get orange stains on her feet and beard - not her eyes though. Two things had changed. 1) I changed her diet slightly (other foods remained the same) from Butcher's to ?.? And where I walked her. In my previous home Lily mainly had the run of a shingle based large garden although occasionally the front garden which was all lawn. Since moving, I have no garden of my own so I walk her on public land that has lots of grassland but filled with endless weeds. So... I have reverted her diet to her original foods firstly to see if it could be that. If it's not her diet then it must be the terraine.. I do hope not because it's practically impossible to correct the whereabouts of her exercise areas.

hi, my westies have this also. The vet thinks its saliva from chewing/possibly irritation from a grain in their food.
We changed to wainrights grain free turkey and veg and what a difference

I have tried grain free, no change. Lily has been fostered for the last 10 weeks as I am shielding. She has just come home but still, unfortunately, has orange feet and mouth.
So from that I deduce that it is not the terrain that she is walking on! Not sure where to go next.