Make alpha, beta and discovery $govuk-blue (#370)
Make alpha, beta and discovery $govuk-blue (#370)

The phase tag is now $govuk-blue (as previously the pink and orange
colours used failed contrast requirements).

Update the Sass variables to also use $govuk-blue.
alphagov/govuk_frontend_toolkit,alphagov/govuk_frontend_toolkit,alphagov/govuk_frontend_toolkit,alphagov/govuk_frontend_toolkit