Fix typo in scales-colour.qmd

scales-colour.qmd

@@ -30,7 +30,7 @@ Fortunately for us the human eye only has three different colour receptors, and
 You may be familiar with the RGB encoding of colour space, which defines a colour by the intensities of red, green and blue light needed to produce it.
 One problem with this space is that it is not perceptually uniform: the two colours that are one unit apart may look similar or very different depending on where they are in the colour space.
 This makes it difficult to create a mapping from a continuous variable to a set of colours.
-There have been many attempts to come up with colours spaces that are more perceptually uniform.
+There have been many attempts to come up with colour spaces that are more perceptually uniform.
 We'll use a modern attempt called the HCL colour space, which has three components of **h**ue, **c**hroma and **l**uminance: \index{Colour!spaces}
 
 -   **Hue** ranges from 0 to 360 (an angle) and gives the "colour" of the colour (blue, red, orange, etc).