A single color can appear as two different colors depending on its surroundings

Albers's foundational demonstration shows that identical colored paper, cut into two pieces and placed against two different background colors, will appear noticeably different to viewers even though the paper itself is physically unchanged, a phenomenon he treats as the central fact any serious study of color must confront. He argues this makes color fundamentally different from a fixed physical property like wavelength, since human color perception is inherently contextual and relational rather than absolute, shaped by simultaneous contrast effects the eye cannot simply override through conscious effort. Albers has students execute this exercise directly with cut paper rather than simply describing the effect, because he believes the shock of witnessing one's own eye be deceived carries far more instructive weight than reading about the phenomenon secondhand. This principle undercuts any color theory built on the assumption that a named color, such as red, behaves consistently regardless of context, replacing it with the more demanding but more accurate premise that every color's effect must be evaluated within its specific surrounding conditions. Takeaway: a color's appearance is never fixed; it is always shaped by whatever surrounds it.