was + to be:
Singular - was ist:
What colour is your dress? (Welche Farbe hat dein Kleid?)
Plural – was sind:
What colour are your trainers? (Welche Farbe haben deine Turnschuhe?)

was + verb:
Objektfrage - wen oder was?
What do you like? (Was magst du?)
Subjektfrage - wer oder was?
What happened yesterday? (Was passierte gestern? )