Overcoat, Back gradients, or the darkening of the spine, is a trait unrelated to genes and can be applied to any design regardless of their genotype.
On Tabbies, the gradient will go under tabby stripes.
The MAXIMUM coverage for Back Gradients is highlighted above.
While the gradient may have such high coverage, it must NOT completely hide the original base color. If the base color isn't obvious, the gradient may be accidentally mistaken for, or interpreted as, the base color and it could lead to corrections.
The back gradient is a trait that interacts with the cat's base color. As a result, back gradients should always be close in color to the base color.
On epi-white and albinos: Back gradients must fall within acceptable white colors.
On silver tabbies: back gradients will lighten with the base coat. Colors used for the back gradient should still appear silver in comparison to the stripe color.
On color points: back gradients will be affected by colorpoint. Back gradients will lighten in accordance to the type of colorpoint.
Epiwhite / Albino
Black Tabby
Silver Black Tabby
Siamese
Back gradients may be:
Hard-Edged
Soft-Edged
Blended
The back gradient can come in various shapes and designs. It can cover a large portion of the spine, or none at all.
Generally, smooth and even edges are strongly preferred, as they appear more natural! Here are some examples of good undercoat shapes.