"The juice is red."
Translation:Le jus est rouge.
At level 7, you have already learned many French nouns. You know that all nouns are gendered and you have translated many sentences with nouns and articles.
If you still don't know these nouns and their genders by heart, please go back and learn them each with their gendered indefinite article: un homme, une femme, un garçon, une fille, une orange, une robe, un livre, une lettre, un menu, un journal, un enfant, une pomme... etc.
Back to your question about the French definite articles:
- "le" is "the" in front of a masculine noun starting with a consonant = le garçon
- "la" is "the" in front of a feminine noun strarting with a consonant = la fille
- "l' " is "the" in front of any singular noun starting with a vowel sound or mute H= l'homme (masc), l'orange (fem).
- "les" is "the" in front of any plural noun.