Fix different text color in unfocused views

[polter-rnd]

Fixes #126

There is an existing hack for keeping unfocused item views not greyed-out, but it seems outdated and not working.

What has been done:

• Update Colors::mix() to be compatible with libsass's mix()
• Compare HexArgb representation of colors instead of floats

[greenbeauty]

Thank you, this fixed the issue for me!

[grulja]

Alright, looks good to me, I didn't notice any major differences, except the fix for unfocused views.