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