Short contact juice and skins.
White grapes.
Long contact juice and skins.
Black grapes.
Long contact juice and skins.
White grapes.
Short contact juice and skins.
Black grapes.
White wine can be made from both black and white grapes.
Example: Blanc de Noirs is a white wine (Blanc) made from Black (Noir) Grapes.
The color is in the skins.
So if the skins are thin or removed before fermentation (short contact), the color will be lighter or white.
Here's a list of Wine Colors.