Yes, but colour is a touchy subject. It's like saying "wouldn't red be just as acceptable" if the correct answer is scarlet. Lilac is a shade of purple like how scarlet is a shade of red, so you're not wrong, but i guess they want the general term
Is "lilla" tone 1 or tone 2? The phrase is also a question so the second syllable of "lilla" sounds high than the first. If I had to guess, I would guess tone 1, but you have no idea how many times I've changed my guess.