iPhone / OpenGLES / FillRect

Hi,
I have some iPhone project working, it draws some images, which works (I had to manually enable GL_BLEND to get transparency to work though)
Now I want to draw a rectangle with an alpha channel, so that the screen is overlayed with a blue tone.
However, nothing works.
Any hints on how to get this to work?
I have some iPhone project working, it draws some images, which works (I had to manually enable GL_BLEND to get transparency to work though)
Now I want to draw a rectangle with an alpha channel, so that the screen is overlayed with a blue tone.
However, nothing works.
Any hints on how to get this to work?