Try playing into your stand as previously suggested. This is the quickest and cheapest way to darken up a bit.
Also talk to your director and see if he/she can be more specific. Saying you're to bright is like you going to the doctor and when he/she asks what is bothering you you say, "I don't know just fix me!"
Maybe after you playing with your bell down a bit; or into your stand a bit more he/she will have the sound from you that is desired.
