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