Brown mascara can have a profound effect on different eye shapes, and it's all about understanding the science of color and perception.

1. Almond Eyes: Almond eyes are considered the most versatile shape and can be enhanced with brown mascara. Brown mascara can add depth and dimension to these eyes without making them look overly dramatic. It can also help to create a soft, natural look that accentuates the eye shape.

2. Round Eyes: For round eyes, brown mascara can help to elongate the eye shape. By focusing the mascara on the outer lashes, it can create a more almond-like appearance. The softer hue of brown mascara is less harsh than black, making the eyes appear more open and bright.

3. Monolid Eyes: Monolid eyes can benefit greatly from brown mascara. The softer color can help to define the lashes without making them look clumpy or heavy. This can create a more natural, wide-eyed look.

4. Hooded Eyes: Hooded eyes can sometimes appear smaller or more narrow. Brown mascara can help to open up these eyes by adding volume and length to the lashes. The softer color can also help to highlight the eyes without drawing attention to the hooded lid.

5. Deep-set Eyes: Deep-set eyes are set further into the skull, creating a more prominent brow bone. Brown mascara can help to bring these eyes forward. By applying the mascara to the center lashes, it can help to create a more balanced, open look.

6. Protruding Eyes: Protruding eyes are more prominent and can sometimes appear overly large. Brown mascara can help to balance these eyes by adding definition and depth. The softer color can also help to create a more natural, subtle look.

7. Close-set Eyes: Close-set eyes are closer together, and brown mascara can help to create the illusion of wider set eyes. By focusing the mascara on the outer lashes, it can help to create a more balanced, open look.

8. Wide-set Eyes: Wide-set eyes are further apart, and brown mascara can help to create the illusion of closer set eyes. By focusing the mascara on the inner lashes, it can help to create a more balanced, open look.

Remember, the choice of mascara color is not just about eye shape, but also about skin tone, hair color, and personal preference. Brown mascara can provide a softer, more natural look, but it can also add depth and dimension when used correctly.