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