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