Plants need light to grow. No duh! Specifically, plants need a certain number of photons of specific wavelengths from the blue and red end of the spectrum to take apart water and carbon dioxide molecules to make more plant. The middle bit is reflected back and so plants look green.
So, do you need those purple "grow lights"? Since they theoretically only put out usable photons, you are not wasting electricity on light that's not being used. If you are a commercial grower, that could be enough money to pay the extra expense of the lights and improve your profit margin. If you have a couple of trays of seedlings, probably not.
What you do want is lights with a high colour temperature. The higher the temperature, the more blue light it contains, and there is typically no cost difference between lights of different color temperature. So look for daylight bulbs which are above 5000K. Daylight bulbs have better colour accuracy so they are typically used for shop lights.