Refresh: Update colour pallette

[stephaniehobson]

Colours have mostly settled so let's do another pass at matching the design colours. See the Figma file. (Note: the hex codes written on the page are wrong but you can get the right hex by selecting the colour)

The existing colour variables will need to be renamed to to reflect these changes. I suggest dropping the light/medium/functional/dark naming scheme in favour of the colour names used in the Figma.

As part of this work please check that the right colour variables are being used for our existing components. In Figma if you switch to dev mode, click an element and look in the right column you can see the colour variables being referenced by the component in the "Selection colours" section.