Sign Meaning blue curve line means clear sky & fresh air. aqua curve line means the cooperation between public and PCD to eradicate pollution problems. green tree good environmental quality comes from pollution control. green linear the near by surrounding such as soil, forest, etc. aqua linear water, better environmental according quality as prosperity of PCD that has responsibility for society and environment . blue color is blue sky. aqua color is good environment. green color is responsibility of PCD.