Colors on frontpage with iframe

I am making a page with Iframes on frontpage. I have a graphic background
for the iframe, made with paint shop pro. then, i made the page to go into
the iframe the EXACT same hex code color (A5A6BF) as the graphic. but, when
viewed in preview, the iframe tone and and graphic tone are not the same.
it appears as if the 2 colors are blending or something, cause when i but
the iframe with the same background color on a white graphic, the right
color is displayed.

So in short, the iframe and the graphic are showing different shades of the
same color, but the right color is shown when i but the iframe on a white
background.

thanks in advance