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