autocomplete: highlight hardly highlights anything

[oliversalzburg]

Actual Behavior:
When using md-highlight-text, the resulting highlight isn't actually highlighting anything. At least the contrast is so low, that hardly any effect is visible.

CodePen (or steps to reproduce the issue): *
You can observe the problem directly at https://material.angularjs.org/HEAD/demo/autocomplete

Additional Information:
Chrome stable, Windows

[mckenzielong]

Looks like the example from the spec uses something close to #b3b3b3 where the autocomplete component is using #757575. Maybe something like background-500 would be a better choice (400 seems too light, especially with hover)