TwentyTen Getting Cell Borders to Show

I am fairly new to WordPress but catching on fast. I wanted to have a colored border on my tables, and figured out how to adjust the CSS for that (yes I created a child theme first!–other great posts had suggested that step). But, now my table shows the color I want around the outer border of the table only. I would like the color to show between cells as in a traditional html table.
Any suggestions as to where I make that adjustment in the style.css for twentyten??

Any help greatly appreciated!