Possible Interpretations:
* Beyond the Spectrum: It could imply colors that are "beyond" the visible spectrum, like infrared or ultraviolet. These colors are not visible to the human eye, but can be detected with special equipment.
* Hyper-Saturation: The word might be used to describe colors with an extreme level of saturation, beyond what is normally seen in natural pigments. This could be interpreted as extremely vibrant or intense color.
* A Combination of Colors: The word could be used to describe a color that is a unique combination of different colors, potentially impossible to recreate with traditional pigments.
Ultimately, the meaning of "ultrachromatic" depends on the context in which it is used. If you encountered this term, providing more information about the source or situation would help determine the intended meaning.