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