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