Whenever I insert a new table, any columns beyond the standard three have permanently gray borders. The thickness changes when I do so under (right click)>Table, but the color will not. The text positioning is also different in these new columns, but I’m able to change that. Anything I’m doing wrong?
I think you’ve encountered one of the bugs in the Apple text system, which is responsible for Scrivener’s table formatting. Your best alternative may be to do final table formatting in another word processor.
In my experiments, I was able to change the borders some of the time, but not consistently.
You should be able to change the borders easily using the table inspector (Format > Table > Table…). As Katherine says, Scrivener uses the standard OS X text system for tables, which always creates tables in grey for some unfathomable reason. When adding new columns, if you use Table > Table > Add Column Before/After (also available in the contextual menu), things should work much more nicely, with columns created with a black border and using the correct formatting. It’s the standard OS X table inspector that always creates new columns and rows in grey.