Final answer:
The information provided does not specify the color of Oralia Bernal's fingernails. The references focus on the use of pigments in artwork and painting techniques. Without further historic documentation or context, we cannot determine the color of her fingernails.
Step-by-step explanation:
The details provided do not specify the color of Oralia Bernal's fingernails. Instead, the references provided describe the different pigments used in her artwork and a general discussion about art and painting techniques. In particular, these references describe the use of natural pigments for colors in painting, a detailed description of another artist using blue in their work, and an understanding that artists might use multiple colors in their creations.
However, regarding the specific color of Oralia Bernal's fingernails, there is no information available that would allow for a factual answer. Such a detail may not be historically documented or it may not be significant in the context of Oralia Bernal's artistic work, thereby leaving us without a clear or definitive answer.
In providing an answer to the student, it would be important to clarify that, while the materials provide insight into painting techniques and color usage, they do not address the precise question about the color of Oralia Bernal's fingernails, and as such, we cannot say for certain what color they were.