Mulching helps, especially if mulching with black plastic, which will not only heat the soil, but radiate heat upward into the pepper bush itself. Moisture also is important. Peppers must have full sun to produce fruit and for fruit to ripen. There's not a whole lot that a gardener can do if blooms begin to drop off. However, we can be heartened by an experiment conducted by Canadian scientists who actually denuded pepper plants of all open flowers through July and doubled their crops for the year.
Most peppers start out green and mature to their ripe color.
There are a few exceptions. Most of the purple ones start out purple and deepen to orange or red if left on the vines. Brown peppers, like Choco or Sweet Chocolate, start out brown and just get darker. The orange Mandarin deepens to a darker, almost-pumpkin color. In the Washington area's temperate growing zones, the most flavorful of the colored peppers are not the orange and yellow, I have found, but the red and purple.