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