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