Quick Easy Flash Question please help

Hiya - my brain has gione dead!

I have a simple logo with two boxes - one blue, one black.

I want the boxes to “swap” colours, so the blue becomes black and black becomes blue.
I’ve tried playing wityh the motion tween and usiung to pre-created images but this isn’t working… any ideas?
Nothing actually moves in the picture, I simply want the boxes to smoothly change colour - but the logo was NOT created in Flash it is an imported file.

I have two .jpg files which are the two “versions” of the logo, i.e. the two possible box-colour-settings.

Please help!