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