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