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)(25,26,31,35,30,37,29,36)(27,32,28,34,39,33,38,40)(1,2)(3,6)(4,5)(7,8)(10,14)(12,19)(15,20)(18,23)(25,27)(26,32)(28,31)(29,38)(30,39)(33,37)(34,35)(36,40) involution — undirected(2,5)(3,7)(9,11)(10,15)(12,18)(13,17)(14,20)(16,22)(19,23)(21,24)(25,28,30,38)(26,33,37,32)(27,29,39,31)(34,36,40,35)(1,3,4,7)(2,6,5,8)(10,14)(11,17)(16,21)(18,23)(25,28)(26,34)(27,29)(30,38)(31,39)(32,36)(33,35)(37,40)(2,5)(6,8)(9,12,13,19)(10,16,14,21)(11,18,17,23)(15,22,20,24)(25,29,30,31)(26,35,37,36)(27,28,39,38)(32,40,33,34)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.