Thank you for your question. The photo doesn't show enough of the frog for me to make an identification. I suspect the orange coloration of the leg is a mutation of some kind. I forwarded your photo to a herpetologist I know to get his opinion.

I'll be back in touch as soon as I hear back from him.  Thank you for your patience.

Jim

Thanks for your time and attention, Jim! I’m curious to hear if it might be a mutation and if that might be indicative of a pollutant. Water quality is very important for the hatchery. 

Hello again. I heard back from my herpetologist contact. He has much more experience with frogs than I do. He believes this is a bullfrog, scientific name Lithobates catesbeianus. They are native to the eastern United States, but were introduced to the western region as early as 1900. Introduction is usually through escapes from aquaculture operations, pet trade, landscape ponds, research and teaching.

Here's a link to the USDA National Invasive Species Information Center's page on bullfrogs:
https://www.invasivespeciesinfo.gov/aquatic/fish-and-other-vertebrates/bullfrog

He believes the coloration on your frog is most likely a genetic anomaly versus a water quality issue.

I hope this information helps, and thank you for contacting Ask an Expert.

Jim