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