hey everybody
i read during avast startup that when avast is registerd and workin properly…it will turn blue…but my avast in the tray is always gray…
i scanned my system thoroughly using avast and it showed no problem…also there are times when my sytem restarts on its own…and also shows many other interruption to running programs…
plz help me out
Welcome to the forums, ravianand. 
Before help can be given, we need more information from you. What is the OS, other security programs, past anti-virus service, etc.
I think this is more a graphics issue, background colour, etc. The avast icon isn’t a royal (bright) blue more a blue grey and the sheen effect makes it look more grey for some.
Provided it doesn’t have a red bar through it and it rotates when files are scanned, the colour is unimportant.
System restarts can be for many reasons, software and hardware, as such this is difficult to pin down. If your screen just goes black and reboots this is more likely to be hardware (PSU, CPU or RAM) possibly heat related since it is Summer.