adjective (a)

• lacking in variety and interest(adj.all)

  Example:
  A colorless and unimaginative person.
  A colorless description of the parade.
  

  Synonym:
  colourless
  

  source: wordnet30
• weak in color; not colorful(adj.all)

  Antonym:
  colorful, colourful
  

  source: wordnet30
• Without color; not distinguished by any hue; transparent; as, colorless water.(adjective)

  source: webster1913