Selected link contrast in FxA signup promo

[janbrasna]

Description

Active link on dark background gets Fx-themed blue treatment and is barely readable.

Steps to reproduce

https://www.mozilla.org/firefox/ (FxA form down the page), move keyboard focus to the plaintext link (sign up, learn more, terms of service etc.)

Expected result

Readable text even when active.

Actual result

Environment

FXDE, WebKit

[janbrasna]

There seem to be issues separately for focus, active, and perhaps visited; as not just blue but also green gets used?