Cornflowers were a particular favorite of the Queen, and cornflower motifs are on many china and other decorative pieces made for her. She also liked violets and roses.
Her favorite colours are more difficult to track, as she changed her preferences during her life. She wore a great deal of white when she took up the simpler fashions of the 1780s, but when she got heavier and her complexion became less dazzling after her pregnancies she reverted to more formal dresses in colours which made her skin look better, giving up pink in particular as she felt it no longer suited her. Her portraits show a lot of blue and red (in her less formal portraits, which would presumably show her preferences more than her state portraits), the colour puce (a sort of pinky brown) was invented for her, but in general it seemed she went for pastels in her youth and stronger darker colours after she turned thirty.