I need to put a symbol on a cake that has a lot of small detail. Thinking about doing it in royal icing but afraid the colors will bleed since it will put on buttercream frosting. Any suggestions for a different method that might work better, not even sure if I can do the small details.

How about a fondant plaque? If you mess up, it's easier to erase and it won't bleed through the fondant.

Chocolate/candy melt plaques work awesome, take ur image and photocopy/scan it so it is reversed, tape a piece of acetate over it using disposable piping bags (u can cut the end as fine/thick as u need it) do ur outlines/details in ur different colors layering the chocolate to fill in ur sections as u go ( i hope i make sense) then when its all done give it one final thick layer of chocolate to cover the entire thing, when it hardens pop it off the acetate and you have a perfect image.hth