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