Layers? Opacity? Bring to Front? What's the problem here...

[Dynamic Office]

So i've got the two filing cabinets set to be at the front,  the grey box with orange boarder is at the back, all are within the same layer and the filing cabinets are 100% opacity.

The grey box has a slight opacity to it but nothing that should cause this, also the reason i've positioned them like this is for example but you can see a clear colour difference as if the pedestals are under the box, see where the grey end and becomes white? see the colour difference?

What the heck is causing this cos' it's driving me mad!

[SJRiegel · Accepted solution]

Do the file cabinet images (or their image frames) have a blending mode applied?

[BobLevine]

I'm guessing multiply.

[Dynamic Office]

...................... I was right clicking effects and not seeing anything ticked, opened the effects panel and behold, multiply = 100%.