Diff colors are reversed from labels

Given the following test:

````js
var  vows = require('vows')
	,assert = require('assert');

vows.describe('something').addBatch({
	'actual vs expected': {

		'should be colored correctly': function (topic) {
			assert.equal('this is the actual', 'this is the expected')
		}
	}
}).run()
````

I get the following screenshot:

![reversed](http://i.imgur.com/v0jgv.png)

This pull request makes it instead look like:

![proper](http://i.imgur.com/l6x53.png)