Recently I had to move my computer tower. When reconnecting the cables I made sure that everything went back (in what I thought) was the right place. However, 3 small plugs may be in the wrong place and I cannot hear any sound. Also, all colours on the monitor are washed out (e.g. everything is pale and yellow flowers are now pale pink). Even after using system restore I cannot fix the display.

Since you cannot hear audio the 3 small plugs which you may suspect are in the wrong place are probably the microphone, line-out (i.e. speakers) and line-in plugs. You may find the plugs and the computer sockets are colour coded, so you know which plug to put into which socket. In the event that they aren’t, you should trace where each of the 3 cables go, so you know which plug to put into each socket. Above each socket on the computer should be an engraved symbol:
‘¢ the microphone symbol means the socket is, obviously, for your microphone;
‘¢ the ((())) –> symbol is line-out, this is for the speakers; and
‘¢ the ((())) <– symbol is line-in. I am unsure what device you would have connected to this socket, but examples of devices are a tape recorder or LP player

Regarding the second problem where colours on the monitor are washed-out, this is symptomatic of the monitor cable not being fully plugged into the back of the computer. Generally when the monitor cable is loose, not all colours will be displayed and the monitor has a tinge (this happened to me last week when a monitor had a strong purple tinge). Unplug the monitor from the back of the computer and positively plug it back in. If you still have the problem, check to see whether any of the monitor pins have been bent (a common problem) which could have happened during removal and plugging-back-in of the plug.