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