These traits are mandatory for vabbits. You must have both a Color and Tone trait present on any design.
On vabbits, the color displayed on the plating reflects the inner flesh which is displayed visually through the vabbit's inner ear, paw pads, and mouth. This means that any Single, Double, or Triple Color traits will apply to colors used in all of these areas.
Pure grayscale, which has equal parts red, green, and blue, and therefore has a saturation of 0, defaults to a hue of 0° in most art programs. In reality, it is the exact same color no matter what degree of hue it is at, with the only possible change depending on brightness/value. Because of this, pure grayscale will fall under Warm Tones by default, if there is no other tone present that would fall under cool tones. Additionally, pure grayscale as a plate/inner flesh color counts as a free color independent of Single, Double, or Triple Color traits.