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