missing table background color style on copying frim html page

You have to extend the Advanced Content Filter settings. For example:

config.extraAllowedContent = 'table{background,background-color}';

Of course it didn't work because it's not the final solution. It allows styles only on table, when in your case they might be added to row or table cell or who knows what else. Please read the docs.

If you correctly clean data in the backend (what you should do in any case), then no. Only user loses because content pasted by him will not be cleared, so it may generate mess.