Use the highlight color instead of the tint color

The tint color of a phone account only refers to the color of the icon,
the highlight color is the general display color used for text,
backgrounds etc. We should use highlight color in InCallUI
Also minor color updates (lightening the "dark" version a little)

Bug: 18192071

Change-Id: I4078897bcb871326a4806f64355a67c5b267e9e6