Question

The ancient Persian philosopher Avicenna believed that looking at the color ________ had beneficial effects.

Answer 1

The ancient Persian philosopher Avicenna believed that looking at the color blue had beneficial effects. 
Avicenna thought that if you looked at something blue, or surrounded yourself with blue color, or wore blue, it would have a positive effect on your health and overall life. It is a fact that brighter colors make people happier, so maybe he wasn't wrong.