a bead border to a cake? I usually just use butter cream but the lady wants a teal bead border. I don't usually use royal much but was wondering if it would be a better choice this time.
I rarely use RI... if you're talking about piping a bead border, I'd use BC.
If you're talking about attaching fondant bead/balls to make a border, you could use either (or if it's fondant on fondant, water will work).
Personally I'd use buttercream. When cut it will go with the cake and royal icing will be hard and crunchy.