This　paper　proposes　an　algorithm　of　BP　neural　network,　which　reproduces　a　color　image　under　D65　light　conditions　by　using　a　pair　of　images　(one　with　no　D65　light　source,　and　the　other　with　D65　light　source).　The　result　of　reproduction　image　which　used　a　fluorescent　lamp　as　an　unknown　light　source　is　presented.　This　algorithm　successfully　removes　the　effect　of　the　unknown　light　source　color　and　achieves　color　constancy　at　a　practical　computational　cost.　The　experiment　results　show　that　the　validity　of　the　proposed　algorithm.