Champagne can be made from a single grape variety of a blend. In most cases it’s safe to assume that your wine is a blend unless otherwise specified on the label.
Blanc de Blancs refers to wines made from white grapes, such as Chardonnay, in particular, when it comes to Champagne. These tend to be crisp and elegant with vibrant orchard-fruit tones.
Blanc de Noirs refers to white sparkling wines made from red grapes, Pinot Noir and Pinot Meunier in Champagne. The juice of virtually every red grape is actually clear so a quick pressing off the skins results in white wines such as these. The flavor of the wines retains hints of red fruits and tend to be somewhat richer than their Blanc de Blanc cousins.