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