Digital cameras have their own screens.
Colour depth and aspect ratio are both important aspects of the final image. The camera screen is not the best place to assess the impact of your shot. Your shot is only a basic representation on the camera screen. You have to judge what a picture looks like before you shoot it. Is it going to be the same after the shot? No, it is a facsimile of the final shot.
The screen on your camera is an indication of what the image will look like. The actual image will probably be processed in an image editor, colour enhanced and possibly cropped. What you see on the camera screen is therefore a basic concept. It’s not an accurate representation. You can find out more about the general issue of screens in… “Of video graphics and cameras”.
Here is a little background to help you understand the idea of colour depth and aspect ratio.
This is the levels of colour that are found in a graphics display. Not just how many possible variations of Red, Green, Blue, (RGB) but also the full range of derivative colours and the tonal variations and brightnesses available. Colour depth involves a huge number of colours – potentially more than sixteen million colours. Not all of these are always represented on the screen on your camera. You should view the camera screen as a less than complete colour range. In addition the image on the screen is compressed to get the picture into a small space. This reduces what can be shown and how detailed it is. So the camera reduces colour and sometimes details. So be wary of what you seen on the screen. Read more about colour depth.
Throughout the history of film, television, graphics and images through the last century aspect ratio has been of importance. The term is used to describe the shape of the screen. Historically a large number of formats for screen shape have been established. Aspect ratio is the subject of a full article in the Photokonnexion Photographic Glossary. The final shape of your picture is related to the aspect ratio of your sensor. Normally that aspect ratio is the same as the screen. However, when looking at your picture in the screen it is worth thinking about your final crop. The crop shape can significantly affect the impact of the shot. So do not rely on the aspect ratio you have been given. When using the screen think about your overall composition in the completed image.