The colour of 100 / 130 grade low lead fuel is:

The correct answer is blue. 100/130 grade low lead fuel is commonly identified by its distinct blue color. This color coding helps in differentiating it from other types of aviation fuels, as it is essential for safety and regulatory compliance in aviation operations. The blue hue signifies the specific formulation and assists pilots and ground crews in selecting the appropriate fuel type, thereby preventing potential cross-contamination with fuels that have a different color coding.

Understanding the color coding of fuels is vital, especially in aviation, where using the correct fuel directly impacts engine performance and safety. The other color options provided are not associated with this grade of fuel and could lead to confusion if not properly recognized.