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