Move the sliders up and down slowly to adjust the background
until it matches the rectangle in the middle
Explanation
A colour is characterised by its red, green and blue components.
You can use these additive primaries to specify any colour
you can get on a computer screen,
any colour within the colour gamut of the monitor.
You can’t get every visible colour by this method—some
colours would require negative amounts of one of the primaries,
which isn’t physically possible—but you can get enough for most purposes.
Observations
The illustration on this webpage is
an actual demonstration not just a simulation—the
colours on this computer monitor really are being produced by the light from
an array of tiny red, green and blue light sources.
Many computer programs provide a colour picker that allows you select a colour
by specifying its RGB values.
Until you are familiar with RGB values,
it’s intuitively easier to select a colour by adjusting
its HLS values.
The Java applet on this page was built with Processing.
