Mood-Boosting Hue: Blue Nail Polish When you can't get outside every afternoon to observe the blue skies on your own? Reach for a polish to give you that same sunny feeling. "I love a cool pastel look to remind you of spring, even if you're indoors," said Logan. This cool-toned colour in particular can be especially effective in promoting rest and relaxation, bringing out your best ideas and intuitive thinking. Image Source: Getty / Flashpop