One vertex per element, one color per generator, with an edge from x to x·s.
(2,6)(3,4)(7,8)(9,10)(11,15,20,31)(12,22)(13,26)(14,17)(16,25)(18,28)(19,35,23,38)(21,34,27,30)(24,37)(29,39,32,36)(33,40)(1,2,4,8,5,7,3,6)(9,11)(10,15,17,31)(12,23)(13,27)(14,20)(16,32,33,29)(18,34,26,30)(19,24)(21,28)(22,35,37,38)(25,36)(39,40)(2,7)(6,8)(9,12,13,25,14,24,28,40)(10,16,18,22,17,33,26,37)(11,19,27,39,20,23,21,36)(15,29,34,38,31,32,30,35)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.