Good choice of music and sound effects, also the visual effect when breaking a block is satisfying.
Adding some sort of visual indicator of which paddle is currently being controlled would reduce confusion for the player, perhaps also an indicator for the corresponding ball. Ideally you could just add a glow effect or something, but that wouldn't adhere to the palette restriction, so you could instead add a rectangle and circle around the paddle and ball respectively, or arrows pointing to them.
It's possible for the ball to be stuck bouncing horizontally against the left and right walls, so you could add an exception to prevent this from happening.
Well done, and congratulations on your first released game!