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