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