Thank you so much for the picture and explanation. He has tan undercoat. I am thinking blue otter, but I will confirm with someone in person. What suggestions do you have for breeding with him? We would like color variety and maybe even harlequins!
Yes, I'd call that an opal. A chocolate agouti (aka amber) doesn't usually have that nice slate undercolor - it's more of a dove gray. A lilac agouti (aka lynx) has even paler undercolor.
I'm guessing that the picture of the ring color is from the belly, so the blue ticking color is missing from the ends of the hairs, but it does show the slate undercolor and the nice tan intermediate ring.
As far as colors for pairing with opal, you have a lot of options. For variety in selling pets, using a broken colored doe will result in about half and half brokens and solids. The drawback to this is that broken colors are not recognized in the Velveteen Lop working standard. Here's the standard as it looks currently:
https://arba.net/wp-content/uploads/2022/04/VelveteenLop.pdf
Likewise, harlequin (and its broken version, tricolor) is not a recognized variety in Velveteen Lops. But for colorful pets, using a harlequin doe with your opal buck
might give you harlequins, but most likely would only give you castors and/or opals and harlequinized castors and/or harlequinized opals in the first generation. In later generations you could produce clean harlequins (black or blue).
Adding both harlequin and broken would eventually give you tricolors.
Opal is an agouti, black-based, dilute, full-color variety. The Velveteen Lop working standard allows for all four base colors of agouti (black, its dilute version blue called opal, and chocolate and its dilute version lilac, called lynx). It also recognizes chinchilla, which is an agouti without the yellowish tan color; the tan intermediate band is replaced by a pearly white color. So you could use any of those colors and come up with nice bunnies.
Red/orange is another agouti variety (look under Wideband group), though it does not show the rings in the fur since the dark color is suppressed. The working Velveteen Lop standard recognizes red, orange, cream and fawn, encompassing both dense and dilute varieties, so breeding a dilute to an orange would not be problematic like it would in some other breeds.
Be aware that dilutes are recessive, so if you breed dilutes, all you'll get are more dilutes. E.g. blue x blue (either blue agouti or self blue) = all blues (either blue agouti or self blue). If both parents happen to carry chocolate, you'd also get lilacs (dilute chocolates). So if you want to increase the range of colors in your litters, breed dense colors (black, chocolate) with your dilutes (blue, lilac).
Breeding a self (solid color with no banding or belly/trim markings) to your opal might produce some selfs in the first generation (in addition to agoutis), or it might take two generations to see selfs; it depends on what your buck carries behind his agouti allele. Like dilute, self is recessive, so if you breed self x self, you'll only get self (i.e. you'll lose the agoutis). But if you breed agouti x self, you'll get a mix either immediately or in the ensuing generations.
Breeding him to a REW might produce that color, if not in the first generation, likely in later generations. Same with BEW (Blue-eyed white, caused by the vienna gene), although the first generation babies would be either Vienna Carriers (VC) or Vienna-Marked (VM), meaning mostly colored with some small-to-medium areas of white on the face and/or body. Both REW and BEW (but not VM) are accepted varieties in the Velveteen Lop working standard.
I would avoid himalayan (aka pointed white) since himis should be self, not agouti.
Take care
