Removing usage of [WPStyleGuide baseLighterBlue].

This [WPStyleGuide baseLighterBlue]is basically a duplicated color from
[WPStyleGuide wordPressBlue]. Removing all instances of it so we can
remove baseLighterBlue from the shared repo and cut down on confusion.
Merge pull request #2268 from wordpress-mobile/issue/remove-duplication-with-colors

Removing usage of [WPStyleGuide baseLighterBlue].