Object drops grey shadow when using colored background

[lazeko]

The objects I placed on colored background always drop soft grey shadow instead of black shadow. It happens on preview mode and when I render. Anyway, it looks normal in white bg.

Thank you in advance

[Ussnorway]

thats not a bug its normal

the 'fix' is to rendor as Psd with a white background then open the file is Photoshop, select the white background layer and change it to the new colour

[lazeko]

I've already changed it to another color in photoshop but it still has grey effect. To fix it is to die cut the shadow area out and change its layer to multiply. It's a long process though. Is there any other way to make it faster? 

[Landshark67]

I have always had this same issue. So much so that I have to turn off the ground plane and add shadows in after the render in photoshop.