create a white rgba / CSS3
The code you have is a white with low opacity.
If something white with a low opacity is above something black, you end up with a lighter shade of gray. Above red? Lighter red, etc. That is how opacity works.
Here is a simple demo.
If you want it to look 'more white', make it less opaque:
background:rgba(255,255,255, 0.9);
Demo
For completely transparent color, use:
rbga(255,255,255,0)
A little more visible:
rbga(255,255,255,.3)
I believe
rgba( 0, 0, 0, 0.8 )
is equivalent in shade with #333.
Live demo: http://jsfiddle.net/8MVC5/1/