Blue flower - that was the desire, the goal in Romanticism.
Yellow flowers - in this story they are the symbol for the inner sun, which is darkened, hidden.
To find it - this requires much more strength, than the boy anticipated. But his strong, persistent wish, his desire to find it, attracts a strong helper.
With kind regards
after having found the master bedroom and the yellow flowers. This dream shows us that the boy can't come to terms with his mother's death. He feels guilty and that's why he has these nightmares. But as he is helped by his mother in the end, we can be sure that she still loves him and has forgiven him whatever he has done.