|Image provided to me by J. Burns of Ghostfire Photography, and are copyright to him|
Gus is a pug/beagle mix, also known by the "designer breed" name: the puggle. His appearance is rather typical for an F1 (i.e. first generation pug crossed with a beagle with no back-crossing, etc.) puggle. Now, what is his genotype?
Most pugs come in a sable coloration, while sable is not very commonly seen in beagles. Most beagles are saddled tan. Since saddled tan is recessive to sable, probability makes it most likely that Gus is an Ayas sable carrying saddle marked.
As for the red seen on this dog, is is moderate in intensity. Pugs are usually quite pale, while most beagles you see will be a quite deep red. As such, Gus is most likely Cce moderate red (dark red carrying pale red).
Gus also has a mask. Fawn pugs are always masked, while beagles never have masks. Beagles do, however, sometimes come in recessive red. As I previously mentioned, however, their most common color is saddle marked which means that only come beagles carry the gene and even fewer express it. So, Gus is most likely EmE masked carrying non-masked.
The last gene that can be guaranteed to be acting on Gus's appearance is the white spotting gene. He has a bit of white on his chest and toes. Pugs are solid, while most beagles are Irish white or piebald. I suspect that Gus is Ssi solid carrying Irish white (expressing residual white) due to these factors.
So, that's Ayas Cce EmE Asi or masked sable with residual white (carrying saddle marked, non-masked, Irish white, pale red).