Calvin Klein's go-to runway nail color is actually the best base coat on the market. Based on the principles of facial foundation, Butter London developed a under-polish that will make your manicure stand out stronger. 

A layer of nude polish smoothes the imperfections from under your nail bed and gives the color an even canvas. For the same reasons you should always use a primer, this too boosts the color velocity.

You can get a flawless basecoat and the perfect nude standalone polish for $18 from Butter London.