Added styling for disabled state on select dropdowns (#1316)

[daveoconnor]

This is adding the styling to match with changes in the #1489 PR which changes the template to display but disable the dropdown on the categorized listing page. It will appear as:

@rbbeeston the category selection dropdown will now appear with text with the same orange as the version dropdown. Let me know if you want that changed or prefer them to be consistent.

Enabled dark/light:

Disabled dark/light:

[daveoconnor]

Thanks Rob, after discussing it, here's what I went with. Let me know if you want them adjusted.

Enabled I thought they looked best if they matched the category links.

Disabled Here I went with slate instead of blue, even sky blue 900 stood out a little too much, tended to draw the eye.

[rbbeeston]

That looks good we need to be sparse on the use of the mustard.