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