Oscar changed colour

Hi,

I bought my oscar yesterday, and in the pet store it was all black,
with red circles.

Now it has some transparent stripes which run vertically all the way
around the fish up to the red circles. Is this normal? The
transparent stripes seem to get more noticable when I go up to the
tank - my oscar is still sulking - he swims when he can't see me
watching him, but when I go near the tank he hides.

Thanks