Plants thrive indoors if they have the right kind of light energy available to them, which they absorb to chemically convert carbon dioxide into sugars in a process called photosynthesis. Specifically, plants best absorb blue and red light in the visible range of the light spectrum. Blue light encourages foliar growth. Red light triggers flower and fruit formation. Certain fluorescent bulbs produce light in these optimal wavelengths.
Blue Light Bulbs
Fluorescent bulbs that cast bluish light have a colder appearance. Cool-white bulbs fit into this category. Most major manufacturers make cool-white bulbs in a variety of sizes and styles, including GE, Sylvania, Philips and SLI Lighting. Light intensity is important to plants; generally a distance of 6 to 12 inches from the light source is optimal for them.
Red Light Bulbs
"Warmer" light gives off more red wavelength, which blooming plants need to trigger the gene expression that forms flowers. While cool light is the more standard light sold in fluorescent bulbs, it's possible to even buy lights that radiate a perceptible pink hue. Don't completely remove the blue lighting from the plant, though. Both blue and red lights are needed to to encourage blooming. All the major manufacturers produce "warm lights," so finding one shouldn't be difficult.
Manufacturers also offer fluorescent lights created specifically to encourage plant growth, though they are usually much more expensive. They give off a deep purple light, or try to offer a full spectrum of white light closely resembling what's available in the great outdoors. Most plants will readily grow under cool-white bulbs; try those before shelling out the extra money for "grow lights."