If it's a default put-pf the box fill, instead save a copy so as not to mess up any placed instances of the existing fill. Edit the copy as instructed.
Erika
Architect, Consultant
MacBook Pro Retina, 15-inch Yosemite 2.8 GHz Intel Core i7 16 GB 1600 MHz DDR3
Mac OSX 10.11.1
AC5-18
Onuma System
"Implementing Successful Building Information Modeling"