impossible color

plural impossible colors

1. A color that the human eye normally cannot see, but might seem to appear under rare conditions or due to visual illusions.

   If you're still with us, there is one last impossible color we’d like to share. Imaginary colors are those that mathematically exist, sure, but we’ll never see them.

   2024 September 24, Tyler Thrasher, Terry Mudge, The Universe in 100 Colors: Weird and Wondrous Colors from Science and Nature, Sasquatch Books, →ISBN, page 228

   1 more example

   Self-luminous red, reddish green, stygian blue, and hyperbolic orange are all examples of impossible colors, a category that also includes chimerical, forbidden, imaginary, nonrealizable, and nonphysical colors. … There are two main categories of impossible color: those that lie just beyond human perception and are impossible to see, but exist, and those that do not exist physically, but we can "see" in the mind.

   2025 May 6, Anthony Dunne, Fiona Raby, “2: An Archive of Impossible Objects”, in Not Here, Not Now: Speculative Thought, Impossibility, and the Design Imagination, MIT Press, →ISBN