Is this possible? I've never seen green and yellow foliage on a violet but they are growing wild in the cemetery across the street. They have very small leaves and dark purple flowers. Is this a find a just a common accident?
Yes it is possible.
But no it is not a common accident.
So it would be very interesting to see a piccy, please Pamela...
Several cultivars are known with variegated foliage (green with white or cream/yellow), eg. 'Rodney Davey', 'Fuji Dawn', 'Dancing Geisha', 'Albo marginata', 'Armandine Millet', The Czar Variegated', 'Marie Giuerin', Quatre Saisons Variegated', 'Tigre Or', arising from various species (eg. odorata, alba, riviniana, selkirkii, variegata, tokubuchiana).
I have also seen variegated leaves on Vv. keiskei, jaubertiana, septemloba?, reichenbachiana, betonicifolia, eg.
In a cemetary, V. odorata is quite likely, though US natives could easily crop up there as well. It would be very interesting to find out which species you have noticed, since I don't think any of the early variegated odorata cultivars are still going. Kathleen Inman has/had a good cream-edged V. odorata, at least a few years ago, but it was not ascribed to a particular cultivar. And I think Bob Brown sourced one from New Zealand a few years back, if memory serves me correctly. But those are very unusual finds. We need a piccy of yours!! You may have rediscovered an old cultivar or found what could become a new one...