If you shade a wildflower with your body, the direct sunlight cannot strike the subject. Instead, the flower is now illuminated by light being reflected from the blue sky above. Since the sky is blue because it reflects blue light, this means the light illuminating on the subject is now primarily blue in content and this will lead to photos with a very blue cast which may or may not be good. On the other hand, sunlight that goes through a thin diffusion cloth does not become more blue. Just the opposite happens.
Blue light is on the short wavelength end of the visible electromagnetic spectrum.
It is high in energy but doesn't penetrate obstacles very well like diffusion cloths. Therefore, some of the blue component of direct sunlight is absorbed by the diffusion material. Normally, this is beneficial, but not always as I will explain shortly. We have encountered problems with photographing blue wildflowers for some years now. In the past, many of the blue flowers we photographed came out pink, lavender, or some other shade that was not blue on film.