A writing board system comprises a white board having a writing surface for receiving a written mark thereupon, a liquid tank filled with water liquid for erasing the written mark from the writing surface, an applicator for applying the liquid in the liquid tank onto the writing surface, and a writing implement having an ink including at least one electron donative coloring compound selected from the group consisting of 2-{2-[4-(dodecyloxy)-3-metoxyphenl]-ethenyl}quinoline, 3-cyclohexylamino-6-chlorofluoran, 3-diethyl amino benzo [a]-fluoran, 3-(4-diethylamino-2-etoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3.3 bis(4-diethylamino-2-etoxyphenyle)-4- azaphthalide, and 3-cyclohexyl methyl amino-6-methyl-7-anilinofluoran, and an electron acceptive developing compound selected from the group consisting of zinc salicylate and bisphenol A.