Crystal Trader

There are two Crystal Traders in Castlevania: Simon's Quest who are interested in trading their crystals for yours. The Crystal Trader in Aljiba will trade you a Blue Crystal for your White Crystal if you possess it. The one in town of Aldora will trade you a Red Crystall for a blue one. Since a crystal traders always trades you a more valuable crystal for a less valuable one, they may be trying to collect them or are ignorant of their powers.