Final answer:
The speaker primarily visualizes d. abstract shapes and colors in their dreams.
Step-by-step explanation:
The speaker in the question primarily visualizes d. abstract shapes and colors in their dreams. This is supported by references to artists like Wassily Kandinsky and Paul Klee, who were associated with the abstract expressionist movement in art, which focused on using shapes and colors to convey emotions and thoughts.
Additionally, the mention of surrealists like René Magritte and their inspiration from Freud's theories about dreams further suggests that dreams can be represented by abstract imagery.