color dependent plot styles are saved in plot style table files with a “ctb” file name extension.you should use this approach if you plan to use the monochrome plot style table for monochrome output devices.this approach is similar to plotting in earlier AutoCAD releases and it is probably the easiest method to understand and use.When you Use color dependent plot styles you map each object to a specific plot style according to the object’s color on-screen. if you create new drawings from a template (or use Saveas) the new drawing will use the same plot style behavior.
if you try to send color output to these monochrome devices your plots may not be of optimum quality.laser printers) produce output using only black ink or toner (i.e. you may want to change some object properties at Plot time (only) and this is what plot styles were designed for.if your plotter can output objects as they appear on-screen (and if this is what you want) then plot styles are not required.You do not have to use plot styles in AutoCAD.
Tutorial how to work With Plot Styles in AutoCAD