One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,4)(5,6,8,7)(9,10,14,20)(11,21,24,17)(12,25,27,31)(13,16,15,19)(18,28,34,26)(22,33,29,30)(23,37,38,39)(32,36,35,40)(10,16,20,19)(11,22,24,29)(17,21)(18,31,34,25)(23,36,38,40)(30,33)(32,35)(37,39)(2,4)(9,11)(10,17)(12,23)(13,22)(14,24)(15,29)(16,30)(18,32)(19,33)(20,21)(25,39)(26,36)(27,38)(28,40)(31,37)(34,35) involution — undirected(5,7,8,6)(9,12,15,28,14,27,13,26)(10,18,16,31,20,34,19,25)(11,23,29,40,24,38,22,36)(17,32,30,37,21,35,33,39)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.