Documentation for `govuk-tint` perhaps wrong

[klssmith]

Description of the issue

I am not sure that the docs for the govuk-tint function are correct. The percentage is described as the percentage of $colour in returned colour. When I've tried this out, a higher percentage adds more white to the colour, which seems to be the opposite of what the documentation suggests. govuk-tint is using mix under the hood, and the docs for that do suggest that the percentage is the percentage of the first colour, which is white in this case.

Steps to reproduce the issue

Actual vs expected behaviour

A style of govuk-tint(govuk-colour("blue"), 25) looks like this:

A style of govuk-tint(govuk-colour("blue"), 75) looks like this:

Environment (where applicable)

• Operating system:
• Browser:
• Browser version:
• GOV.UK Frontend Version: