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