Leave it to the most optimistic season on the calendar to show off the bright side of life. Designers are ordering their collections sunny side up this spring with a cheery pop of yellow that ranges the color spectrum from lemon to mustard to a mellowed-out pastel. Herve Leger offered up a flash of citrine in the best way designer Lubov Azria knows how — on a tantalizing, bodycon dress embellished within an inch of its life. Michael Kors deftly worked the color onto a sheer tulle midi skirt by way of floral appliqués. And then there was Lela Rose, who splashed the golden shade onto a floor-sweeping gown. Color us happy, folks.