Are there any kind of rules against me repainting the symbols on both my attack dice and my defense dice??

I ask mostly because I am one of "those kinds of gamers" that does not like to use other players' dice and want to make sure I get all of my own dice back if they get mixed... Silly superstition, I know... but that is how I roll - no pun intended.

From the Tournament Rules:

Players may mark dice with a permanent or indelible marker to indicate ownership in an unobtrusive manner, but cannot otherwise alter them in any way.

So if you're talking about casual play, anything within reason is probably okay. In sanctioned tournament play, you'd probably be better off with a small mark than repainting multiple faces.

My suggestion would be to avoid paint as it could open you up for potential protest regarding adding weight to a particular side. I would use a Sharpie permanent ink marker instead as there's going to be no weighting bias at all.

You may also consider buying a dice rolling tray. Then you don't have to worry about dice rolling across the table and mixing in with your opponent's. They make some nice ones with a felt bottom.

This will also prevent any instances of cocked dice, which can be frustrating for both players.

Or a dice tower. That tends to keep dice contained too.

My suggestion would be to avoid paint as it could open you up for potential protest regarding adding weight to a particular side. I would use a Sharpie permanent ink marker instead as there's going to be no weighting bias at all.

I have repainted the pips on many dice over the years, mostly to make them easier to see, and it has not unbalanced the dice in any way. I thinned the paints down to a wash, and used an extremely small brush to add only the thinnest of coats.

A wash would put you in the clear at my events, Magnus.