Added Parts Different Colour than Older Ones

[MMH]

Hi there,

I'm currently trying to make a set of instructions for some Lego models I have created in MLCad. I would like to format them so that parts that were added in a previous step are differentiated from the new parts (preferably by making the older parts lighter while the newer ones are in full colour). Is there a way to do this in LPub or MLCad, or is there a better software solution to fit my needs?

Thanks for your time!