1) "...In crystals, molecules are packed in such a way that their interactions are strongest. When you add some other compound it stretches the crystal lattice, molecules are not in optimal positions and their interactions are weaker, thus less energy is required to break them apart." I copied this from the physicsforum.com forum posted by a poster named Borek.
2) According to Wikipedia:
"The colour of iron(III) chloride crystals depends on the viewing angle: by reflected light the crystals appear dark green, but by transmitted light they appear purple-red."
I hope your questions are answered.