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