The ‘blue’ and the ‘green’ hues in the believe it or not image were one color posing to perception as two – because their neighboring hues affected the way the brain ‘read’ their wavelengths of energy.  The way the eye/brain actually reads things as they juxtapose and relate to their contextual influences as well as the projections from our memory is endlessly fascinating.  It isn’t difficult to imagine how significant this effect is for artisans who work with color in any way.

Color is a true magician.  In this image we are tricked into believing its tonal qualities appear to be different.  It’s called ‘the spreading effect.’

image source – Art and Illusion by E H Gombrich

One tone of red and one of blue are the only colors used.  No one has been able to explain why, when those hues are juxtaposed with black or white they appear to be different tones.  It seems that “we see the whole pattern as one and attribute its total brightness or darkness to its elements.” (*)  We don’t see the ‘ground’ as an isolated spread of color, and we can only accept that the colors are really unbroken stripes of a single tone by tracing a path along the strip. 

(*) Gombrich, E. H. (1988) Art and Illusion (Oxford: Phaidon)

This example of just how stitched-together our version of reality really is, comes from the e-book
believing is seeing … the amazing artifice of perception
Artifice is the clever use of tricks and devices. (Collins Dictionary)

It’s one of nine free e-books in the series: empty canvas: wondering mind

You can download them at the wonderingmind website