I've noticed that some viable viola seeds are normally white. However, if you pop the pods early, it depends on how early, but if you pop them much too early (ie. no sign of it being close to being ready), most likely they aren't viable yet. If they are close to being ready, then there's a good chance some of them would still be viable. If you didn't pop them too early, they can still mature a bit, but if you did, then they will not mature, as they need the nutrients supplied by the parent plant.

The ripening happens very quickly but usually the seed should be brown before considered viable. This means the pod should start to split of its own accord.
A little trick with violas and pansies is that the seed pods turn their heads skywards just before they split to dispel seed. You need to watch carefully or alternatively you can make little nets of old panty-hose secured with pins or tiny craft pegs, and these may catch stray seeds that you otherwise miss,

I took some seed pods from mine over the weekend and the seeds were mixed, some were brown and some were white.