HiI'm new to autocad and at present am using 2008.Is it possible (and how do you do it) to change the construction line colour (so you don't have to change layers) and add ruler markings to the construction lines to help set out a drawing.Any help, pointers to help videos, etc, would be much appreciated.Cheers

You can't.  You have to make a layer current before you draw the construction line, or go back and change the properties of the construction line.  You could easily create a custom command that will set a layer current then starts the construction line command.  Do this in the CUI.