noun, feminine/ˌmaɾka ˈblanka/plural: marcas blancas
marca blanca is feminine in Spanish.
store brand (US), own brand (UK), house brand, private label, private brand, white label
“Los supermercados están luchando contra las marcas grandes con productos de marca blanca.” — Supermarkets are fighting national brands with private-label products.
Literally, “white brand”.