a. you dont have to know it.
b. first u have to determine which way is exothermic and which way is endothermic.
If the pressure increase it swings to the exothermic side, decrease- endothermic.
If temperature increases it swings to the endothermic and exothermic if decreases.
WHen you have determined this just figure out the actual coulors of the substances that side has SWUNG TO. Remember according to the LE chatt(somthing) principle, it initially opposes this change, and then swings to this side.
For eg :
A+ B > C (exothermic reaction)
If say A is red and C is colourless
and you increase the pressure, according to my notes, it would swing to the exothermic side, therefore it would BECOME coulourless(c), again, it would initially become red b4 becoming coulourless as it partially opposes this change.