Final answer:
Rihanna is likely experiencing synesthesia, a condition where senses are crossed, as a result of taking LSD, a hallucinogenic drug that alters sensory and perceptual experiences.
Step-by-step explanation:
The effect that Rihanna is experiencing while under the influence of LSD is known as synesthesia. This is a condition where one sense is simultaneously perceived by one or more additional senses. Such mixed senses may include "seeing" sounds or "hearing" colors. LSD, as a hallucinogenic drug, can cause profound alterations in sensory and perceptual experiences, often leading to this kind of sensory crossover. The intensified feelings and sensory experiences, such as brighter colors and sharper sounds, are characteristic short-term general effects of hallucinogens.