Vabbits contain a lot of heat, so their plates tend to have warm tones as well, though there are colors that do not seem to fall under warm tones regardless. Cold tones specifically, however, are rare.
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.