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