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