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