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