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