Allow swatch override of individual colours

When using product-specific swatches, I would like to override individual colours of a swatch rather than being forced to pick all colours. For example: If I have set a global swatch for three colours as: Black: #000000 White: #FFFFFF Red: #FF0000 I would like to override only the red colour for a specific product, while leaving Black and White as they are. Currently, I need to select all colours. So I guess the logic would be: If the global swatch = colour, AND product-specific swatch = colour, then inherit global colours and allow user to override specific colours.