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