Plotting question??

I'm doing structural drawing. I inserted some architectural lines for reference and I want them to be plotted in grey or lither mode. I go into ctb file and I change the screening for particular colour. All arch lines and solids are plotted lighter but they jump on foreground, so other lines which should be darker are wiped out when intersect with lighter lines.

I hope you understand what I'm talking about

How to fix it?

thanks