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)(11,16)(12,24)(13,17)(14,28)(15,19)(18,30)(20,31)(21,37)(22,25)(23,33)(26,27)(29,40)(32,39)(34,38)(35,36) involution — undirected(2,5)(3,7)(9,11,15,23)(10,16,19,33)(12,25,17,31)(13,20,24,22)(14,29,30,36)(18,35,28,40)(21,38,39,27)(26,37,34,32)(9,12,13,10,15,17,24,19)(11,16,22,25,23,33,20,31)(14,26,27,18,30,34,38,28)(21,32,29,35,39,37,36,40)(2,5)(6,8)(9,13,15,24)(10,17,19,12)(11,20,23,22)(14,27,30,38)(16,31,33,25)(18,34,28,26)(21,36,39,29)(32,40,37,35)(1,3,4,7)(2,6,5,8)(9,14,13,27,15,30,24,38)(10,18,17,34,19,28,12,26)(11,21,22,29,23,39,20,36)(16,32,25,35,33,37,31,40)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.