Final answer:
Lorenzo's shade will be a darker green because he adds more blue food coloring than Mariana, resulting in a darker shade of green.
Step-by-step explanation:
Lorenzo and his sister Mariana are mixing colors for decorating a gingerbread house. They are using yellow and blue food coloring to make an icy green color. Since both are using the same amount of yellow but Mariana adds less blue than Lorenzo, Lorenzo's shade will be a darker green. When mixing colors, adding more blue to yellow will result in a darker green, whereas using less blue results in a lighter green. This is an example of color mixing, specifically the subtraction of light, which is a part of the study of colors in Chemistry.