Harlequin exists in other breeds. If bred to another carrier you could get more harlequin or you'll just get whatever the dominant color of the rabbits is. Much the same for the others. Dutch to another rabbit carrying the pattern gives you dutch pattern (for the most part) and to any breed/rabbit not carrying it gets you whatever the dominant colors are. So a black dutch to a black not carrying dutch will mostly if not completely get you blacks. There is a loss of pattern quality for both colors though. Your harlequin markings are less likely to match up and your dutch markings might have weird narrowed, widened, or completely missing sections. Those colors tend to be isolated and have become their own breeds because of the detail required to get the pattern.
Tan is a different matter. It is just an otter/marten but modified much like rex have modified chestnut to castor. You'd have to breed the same modifiers in to get the color but part of what makes tans so striking is also their type. They are a running breed instead of the usually more common commercial and compact breeds. You may get some very oddly shaped rabbits and the pattern does not look the same on a low sitting commercial rabbit as it does on a running breed even if you manage to salvage the right modifiers.
