Bootstrap v3.0.3 and higher has changed its icon glyph from an image to a font, which has several benefits, including the fact that they appear smoother, and can be adjusted easily in size and color the way you would adjust a font. You can download Bootstrap here:

For example, I can display KPIs in color using Bootstrap’s built-in classes (text-success, text-warning, text-error):

Success: <i class=”glyphicon glyphicon-minus-sign text-success”></i>

Warning: <i class=”glyphicon glyphicon glyphicon-exclamation-sign text-warning”></i>

Error: <i class=”glyphicon glyphicon-plus-sign text-error”></i>

And the result looks like this:

The following is a reference of all of the glyph classes available in Bootstrap v3.0.3: