Chestnut (AKA agouti) and broken chestnut. Agouti is one of the dominant colour modifiers and is often what REW and Californians are under their white coats.
Most Californians I hope, would be self blacks, because an agouti based cali has "markers" that may dq it on the table. A lot of NZ's seem to be agouti though. Your broken chestnut looks like he has a lot of rufous mods. very pretty!
I have only had pet stock Cali's (4 in my life, I'm not a fan ) and when crossed with black NZ got agouti, steel and black. I am sure show stock would be black as the points would be the best quality, but all of my does were very faintly marked.
Rufus modifiers are another coat colour altering gene. Fawn, orange and red are genetically the same and it is the Rufus modifiers that determine how deep or dark a red they will be. To be a good dark red they need at least 3 but more is better.
They are added to a genome as '+' marks
for example : "A_ B_ C_ D_ ee ++++ " would be a dark red and " "A_ B_ C_ D_ ee +" would be a fawn