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