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