hi…
I want to use following image box style…
but when I want to use this it’s not high quality and not good feeling about this… the default bar of GUI is great for me… can I use the default box but change it’s color to purple or blue instate of black?
Yes. http://unity3d.com/support/documentation/ScriptReference/GUI-skin.html
http://unity3d.com/support/documentation/ScriptReference/GUISkin.html
you can override the default GUI skin as DaveA points out. But you can also just access the parts of the skin through GUIStyle
http://unity3d.com/support/documentation/ScriptReference/GUIStyle.html
You create a variable of the class/type GUIStyle, assign the wanted image/properties and then apply it to the object you want it on.