"Can you suggest and share some custom made CSS examples that make Perl Monks more pleasing to the eye and easier to read ?"

The "PerlMonks CSS Examples" page might be a good place to start.

There's also a "Theme Configuration". I picked one that was close to what I wanted, then only needed minimal CSS to customise that further.

There's also many Settings pages to customise a variety of things that change to look and feel of the site.

As ww already alluded to, customising the site is for registered users; as an Anonymous Monk you'll just be presented with the default settings.