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