Ink is a skeleton with out a soul, he drinks this vials to get emotions,
Yellow is happiness, red is anger/rage, Purple is regret , green is jealousy , cyan is , blue is sadness  , orange is hopefulness , pink is love/lust  
 and his paint vials also gives him his powers with ink,
he has a terrible memory and he writes stuff he needs to remember on his scarf,
he can't remember his past, 
he as the fear... of whiteness, of absence of presences or shapes around him, loneliness, huge empty spaces, 