You asked about the genetics. There are several genes at work here. Each rabbit gets two copies of each gene, one from each parent. A dominant gene is boss, it only needs one copy to muscle in and take over, recessive genes will need both copies to show. Let's start with the ABCs.
A is for agouti. This is wild rabbit pattern, with several different bands of color on a single hairshaft, usually white eye rings, white belly, a fawn (yellow) triangle behind the ears. The bands are of the main dark color (blue in opals, chocolate brown in chocolate agouti, light brown in lynx; chestnut agouti is the oddball, mixing the gray from the black with some yellow to make chestnut, aka castor) on the outside of the hair, then a yellowish band, then the base color. Agouti is the dominant choice, non-agouti (aka self colors like black, blue, lilac, chocolate and tortoise shell) is the recessive option.
The B gene is for Black/Brown. Black based color (dominant, which includes black, blue, opal, castor). The recessive is chocolate based color (chocolate, lilac, lynx, chocolate agouti).
C is for Color, this is a cascading series of five options. The most dominant is full color--think of all the agouti rabbits, the self colors, torts. Next down we come to your buck--this is chinchilla. Chin takes the normal agouti coat, and removes all the yellow shades. So black chin is just a normal castor without the yellow to make the outside of the hair gray instead of chestnut, and the middle yellow band pearl white instead of fawn. Often, the eye color becomes gray, blue-gray, or blue like your buck. The other options on the C gene are sable, Californian/pointed white/ Himalayan pattern with an all-white coat and dark points, and finally albino red-eyed (aka ruby-eyed) white.
D is for Dilute/Dense. Dense is full color, and dominant. Dilute is the recessive, where the color is paler than normal (black becomes blue, chocolate becomes lilac, orange becomes fawn/cream).
Lastly, E is for Extension, and describes how the agouti bands of color extend along the hairshaft. This is closely related to the A agouti gene, because it determines how the agouti pattern appears on the hair. The most dominant choice here is also quite rare, only found in a few breeds. It is called Dominant Black, and it spreads the outer dark band all the way down the hairshaft, so the rabbit looks like a self black. Next is steel, where the middle yellow band is pushed way out to the tip of the fiber, making a yellow (gold) tip, which is why they are called gold-tipped steel. If you add chinchilla to steel, the yellow becomes pearl white, and the tip becomes silvery--hence silver-tipped steel. The normal rabbit color, with normal agouti extension of bands is next, followed by the choice you see in your kits.
This is harlequin. Here, the yellow and dark bands of color are on separate patches of skin instead of bands on a single hairshaft, making those stripes, splotches and bands of color. The division of color down the middle of the face and middle of the back are common here. If you add in the chinchilla gene, the bands become white and dark, instead of yellow and dark. That would be the case with your buck.
The last choice on this gene is the most recessive, called 'non-extension'. This is the opposite of the most dominant choice, that extended the dark all the way down the hairshaft. In non-extension, the dark is a non-starter, and the yellow extends all the way out. This makes red/orange/fawn/cream agouti rabbits, with the yellow tone all over the body. In non-agouti self colored rabbits, you end up with tortoise shell, where the main body is the yellow shade, but the cooler points (ears, head, tail and feet) still retain their dark color. This is what your doe is.
So, you bred the most recessive choice on the E gene (non-extension) to the next most dominant choice (harlequin, your buck is a chinchilla harlequin--called 'magpie'). Not a surprise that the more dominant harlequin appeared in both kits. The doe had the more dominant full color to the buck's chinchilla. Again, not a surprise the more dominant color won out in the kits--you have full-color harlequin kits.
