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)(11,20)(12,17)(13,28)(14,18)(15,19)(16,24)(21,22)(23,35)(25,27)(26,33)(29,31)(30,34)(32,38)(36,37)(39,40)(1,2)(3,6)(4,8)(5,7)(9,10)(11,21)(12,25)(13,18)(14,28)(15,19)(16,24)(17,27)(20,22)(23,32)(26,34)(29,31)(30,33)(35,38)(36,39)(37,40) involution — undirected(9,11,13,24,15,22,14,29)(10,16,18,20,19,31,28,21)(12,23,27,38,26,37,30,39)(17,32,34,35,33,40,25,36)(1,3,5,4)(2,6,7,8)(11,22)(12,26)(16,31)(17,33)(20,21)(24,29)(25,34)(27,30)(1,4,5,3)(2,6,7,8)(9,12)(10,17)(11,23)(13,27)(14,30)(15,26)(16,32)(18,34)(19,33)(20,35)(21,36)(22,37)(24,38)(25,28)(29,39)(31,40)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.