Final answer:
The artist of 'Untitled (Nehi Bottle on Car Hood)' is not specified in the provided resources. Considerable clarification is required, as many artists, including Donald Judd and Nathan Oliveira, have produced untitled works. Additional context is essential for proper attribution.
Step-by-step explanation:
The artist who created Untitled (Nehi Bottle on Car Hood) within the Los Alamos Portfolio is not mentioned in the references provided or widely known. However, when addressing inquiries about untitled artworks by various artists, it's crucial to identify the correct creator as multiple artists have created works titled 'Untitled'. For instance, Donald Judd is recognized for his minimalist sculptures such as Untitled (6.8.1), fashioned from materials like copper and demonstrating progressive sizing techniques. Similarly, Nathan Oliveira, known for his Bay Area Figurative Movement involvement, and other artists have made significant contributions to the art world with their respective untitled series. If the artwork relates to a specific time, place, or artist's oeuvre, additional details may help in accurately identifying the creator of 'Untitled (Nehi Bottle on Car Hood)' among these diverse works.