A cleric cannot cast spells with an opposed alignment descriptor
Taken from the Cleric description in 3.5 SRD - similar rule appears in PHB:
Chaotic, Evil, Good, and Lawful Spells
A cleric can’t cast spells of an alignment opposed to his own or his deity’s (if he has one). Spells associated with particular alignments are indicated by the chaos, evil, good, and law descriptors in their spell descriptions.
So as an evil cleric, or a cleric of an evil deity, your character is forbidden from using any [Good] spells.
I'm not aware of any rule prohibiting an evil cleric to cast spells with the [Light] descriptor.
Regarding spell descriptors...
I recommend you read the SRD text about spell descriptors. It isn't very long, and says (among other things):
Most of these descriptors have no game effect by themselves, but they govern how the spell interacts with other spells, with special abilities, with unusual creatures, with alignment, and so on.
For example, spells with the [Good] descriptor have special effect on certain evil outsiders, can't be cast be evil clerics, and can be detected using the Detect Evil spell. Similarly, some creatures (mostly undead and darkness-themed) are more vulnerable to [Light] spells.