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