It uses vivid colours such as red to bring home the artist's feelings about what he is seeing. Klee is known as an Expressionist artist and he plays with colour as it suits him in this piece.
Klee often worked with watercolours. Presumably this medium lent itself well to the way the artist chose to express himself with line and form. His Flowers in Stone are not realistic. Instead, Klee sticks to his Abstract roots with the piece, seeking to draw out a response to the softness of flowers against a hard surface like stone.
Flowers in Stone features living creatures which are thriving in an environment that many would not consider ideal. They bloom against the odds. Klee's work brings the hardness of the surface to mind, as he creates texture using light layers of pigment.
Klee's background as a draughtsman can be seen in this piece. The lines are solid and distinct. The overall layout would be well suited to repetition through modern or more traditional methods of reproducing artwork. It brings to mind the paintings of Warhol in this way.
Each flower in the stone is represented by a symbol. Perhaps the symbol chosen for each bloom is indicative of how Klee responds to its shape.
The background around them actually seems brighter than the flowers. This may be a reminder that although the flowers are blooming, they are not blooming as brightly as they could because of the substrate that they are trapped in.
While the background, which is rich in hues of red and orange seeks to overwhelm the flowers, it also draws attention to them. It defines the space that they are in more richly than a lighter shade would. Klee has added to their beauty with this choice of rich colour.
The artist experimented a lot with colour and often chose to use blends in ways that deliberately pulled attention to a particular aspect of the piece. He taught and wrote extensively about coluor theory while he was alive and sought to use colour in a highly individual way in his paintings.