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