all clear plastics will reflect light to a certain extent. i use a special type of polycarbonate i have shipped in from another state and i've never seen it in black or even smoke.
It's an AA. It's nice as far as lids go. I got it for free. Maybe it's just lids in general. I haven't covered a tank in thirty years.
I just think black acrylic would look miles better as it wouldn't glow. It reminds me of those fiber optic sprays that were popular in the '70s the way the light it's transmitted to the edges.