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