The NoDo introduced a very peculiar problem in the HTC and Samsung WP7 devices – it forced the apps and games to use only 16 bit colors irrespective of what the display was actually capable of rendering. Microsoft said that it is the fault of HTC (in case of hTC Windows Phones) that they upgraded the color depth to 32 bit. This was outside the design requirements of Microsoft which are just 16 bit (65k colors). So, HTC reduced the color depth to 16 bit in the March update (Nodo update).
Some experts are predicting that this so-called issue will be resolved in the WP7 Mango update (called Windows Phone 7.5 by Microsoft).
If you cannot wait till October (which is the expected release date of Mango), you can add these 3 registry keys and make the operating system use the usual 32 bit color depth.
HKLM\Drivers\Display\Primary\PrimBPP dword 32
HKLM\Drivers\Display\Primary\bpp dword 32
HKLM\Drivers\Display\Primary\PanelBPP dword 32
If you happen to own an HTC device, you may change the last one’s value to 24 incase you face a degradation in performance.
To do the registry update, you will, of course need a registry editor. If you use a Dell or HTC device, use this WP7 registry editor. If you happen to be user or Omnia 7 or Focus (i.e. Samsung Windows Phone devices), use this registry editor which is said to be working on these devices.