An Add Layer button is is provided for some V-Ray materials, including GenericFlakes 2. You can select an additional layer that can add up to the appearance of the material. Note that the added layers can be removed and rearranged, as shown on the Materials page.
The context options of the Color Slot allow to Copy and Paste a color from one color slot to another, as well as to reset the color selection.
A Reset option is provided in the context menu of each Number Slider. You can reset the slider value to the default one.