Dribbles of blue can easily be achieved in early spring. Possibly the best time to plan and plant for the elusive color, the gardener's Holy Grail, true blue. There are a few choices for later in spring, say amsonia, larkspur, and a few rare salvias (that are blue, not purple), but the blue of early spring can be rich and vibrant, standing alone without competing greens.
Spring bulbs play a major role. Various grape hyacinths or muscari do a great job in March and early April. Small single and double flowering varieties can be inexpensively planted, almost thrown into the garden in fall when the bulbs are for sale. Although it can't go without saying that they are persistent enough to loose all of their charm come May, when the straggly post flower foliage is far from beautiful. A robust covering of foliage from taller perennials is the best way to cover them up, and they don't seem to mind, flowering with gusto the following spring.
Another little bulb with glorious blue flowers are the spring starflowers or Ipheion uniflorum, the latter meaning single flower, as there is only 1 flower per stalk. A minor bulb, the size of a marble, there are several hybrids and shades of blue. Sometimes the palest blues are the most effective, especially in the company of royal blue.
In perennials the low growing veronicas flower early and provide a skirt for the minor bulbs to cozy up to. Commonly called speedwell, this derived from a bouquet of blue flowers given to travelers to wish them "speed well". My favorites are Veronica austriaca 'Crater Lake Blue' or V. 'Venice Blue', both superior for that rich, rich blue color. Ground hugging in habit of growth, they can tumble over a wall, be scattered in a rock garden or edge the front of the perennial border. This wash of blue options can stand alone or be punctuated with Euphorbia polychroma (chartreuse flowers), or Sedum 'Angelina', which has chartreuse foliage accented with orange in early spring.
All of these can also be the filling for planters, add a pansy that is truly blue, or maybe some lobelia to hang over the edge. Early spring is the best time for noteworthy blues, so don't wait for the perfect delphinium, or iris, think March and April.