Koinobori, traditional decorations for Children's Day in Japan, are cloth or fabric carp shapes hung on poles to flutter in the wind. Typically, they come in three colors: black, red, and blue, representing the father, mother, and child, respectively. This symbolism stems from the legend that a carp transforms into a dragon after climbing a waterfall, making it a symbol of perseverance and success, which is why carp were chosen as the motif for these decorations.