In the RGB colour system it is not possible to have negative colour values, because each represents an amount of light, a number of photons if you will, to emit, and you cannot have negative photons.

What do negative RGB values mean?

This means roughly half of all “black” noise will make pixel values with negative components. … In any RGB encoding space, negative values simply indicate that a pixel value projects outside of the triangle formed by the RGB primaries of the encoding gamut.

Are there negative colors?

A negative image is a total inversion, in which light areas appear dark and vice versa. A negative color image is additionally color-reversed, with red areas appearing cyan, greens appearing magenta, and blues appearing yellow, and vice versa.