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