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