Supernova skins are the skins painted with a multi-colored hydrographic. Blue and orange are the dominant colors, dotted with small concentric circles and hexagons. Only one weapon skin belongs to this family, and it's P250 | Supernova. It's been around since the 2014 Operation Breakout update when it was added to The Breakout Collection as a workshop submission. It's one of the 15 or so random rewards you might receive when opening Operation Breakout Weapon cases. It can appear with any exterior except for Well-Worn, and can also optionally come with a StatTrak component.
The exterior and the StatTrak component are also what determines the value of Supernova skins, which range from half a dollar to a few dollars.
Check out other CS2 skins families: