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