Analogous
Colours that sit next to each other on the wheel. Nothing argues, nothing vibrates, and the picture is held together by one continuous condition of light instead of by contrast.
Where the word comes from
Unlike complementaries, this is a modern scheme name rather than a studio inheritance — it belongs to the family of harmony formulas that colour educators derived from the wheel in the nineteenth and twentieth centuries. What it describes, though, is one of the oldest ways of unifying a picture: restrict the palette until every colour in it shares a common parent.
In the studio
Monet's series paintings are the clearest demonstration. The grain stacks and the Rouen façades hold one motif still and change only the hour, so each canvas becomes a study in adjacent colours — the pinks, oranges and ochres of one particular light, with no cool opposite allowed in to break it. Whistler went further and named his pictures for the scheme rather than the subject, calling them nocturnes and arrangements in blue and gold, which infuriated critics who wanted a subject and got a chord.
Why it matters
An analogous scheme has no safety net. Where complementary contrast can carry a weak composition on hue difference alone, adjacent colours are nearly identical in hue, so all the separation has to come from value. Get the values wrong and the image goes to mush — which is exactly what happens to most attempts, and why the good ones look effortless and are not.
Today
It is the default register of anything that has to be looked at for a long time without exciting anyone: dashboards, reading interfaces, long-form layouts, the colour grade of a film that wants an atmosphere rather than a mood swing. The discipline is the same as Monet's. One light, one family, and all the work done in the values.
Pigments used: Ochre · Sienna · Naples yellow
See also: Claude Monet · James Abbott McNeill Whistler · Rothko