From 1982 300D Electrical Troubleshooting Manual:

15R: GN/RD from Fuse 4.
50: VI/WT from Start Lockout Switch
30: RD from light switch
15X: RD/YL from Fuse 8
30: RD from light switch
15: RD/BK from Fuse 12
P30: GN/WT from light switch