The word for ‘white’ in French is ‘blanc’.
In French, colors agree with the noun they modify in gender and number. Since ‘blanc’ is the masculine singular form, if you were describing a feminine noun, you would say ‘blanche’, and for plural nouns, you would use ‘blancs’ for masculine and ‘blanches’ for feminine.
For example, if you want to say ‘white house’ in French, you would say ‘maison blanche’ because ‘maison’ is feminine. If you want to say ‘white cars’, you would say ‘voitures blanches’ since ‘voitures’ is feminine plural.