How to change graph lineStyles?

the user gives the function a figure with 3 graphs ( 3 plots) in it. I want to change the line color and LineStyle of each one. How can I do it? I've tried findobj(gcf,'type','line') but for example in a figure with 3 graphs, it finds 16 line objects. How can I find out which ones are the graphs? Note that the user will give different figures to the function. so I cant not count the lines and try to find which number is for which line.

[Walter Roberson]

Do the figures sometimes have legends? Each legend entry requires a line (or is it two lines? I would need to check.)

[Mohammad]

sometimes they have legends too, but I can't count on it!

Answer 1

[Sean de Wolski]

plottools on

Then interactively change the line styles as you see fit.