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