Radio buttons could use some more contrast

[jvanasco]

originally in #1227

Here's an example illustrating the radio buttons with adjacent colors that are both identical and different.

The state change is barely noticeable when different background colors are combined.
The state change is poorly noticeable when the same background colors are combined.

http://www.bootply.com/119132

Using colorhexa.com / color-hex.com , I tried dropping down the background colors to an 80% tint (from 100% of the current color, which I know is calculated by LESS ). At that setting, all button states were clearly identifiable. Even at 90% it was better ( though not as clear as 80%).

I couldn't figure out where/how to control that in the LESS file, so I couldn't make a patch to illustrate.

[mdo]

Word, I'll take a look. Looks rough in a setup like that for sure.

[mdo]

I've darkened them just a bit, but not too much. Ultimately if you're customizing the buttons, you could easily add a gradient to give the right amount of emphasis. We don't do that because that's too prescriptive.