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