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