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