2 things
  1. CDS usually have high impedance, but the PIC require a max of 10K. You'll need to use a buffer in between (op-amp, transistor, FET, ...)
  2. The way you have it now, you read PORTB and D and place it in your LIGHT variable

try
Code:
        PORTB = (LIGHT >>2)
        PORTD.6 = LIGHT.0
        PORTD.7 = LIGHT.1