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