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