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