Rainbowfish are one of the most unsung yet WONDERFUL fish to own. As mentioned above, they don't look that great at the LFS and they are usually small. But wait until they grow. I have Boesemani and he is almost 4-5 inches in length and beautiful. I also have a red Irian and IT IS RED. I've just purchased a couple of blue rainbows and expect them to grow and color up as well.
They are good swimmers, usually mid-tank and hardy once established. They will eat almost anything and LOVE shelled peas. Using a good fish food and, again as above, a well-planted tank..well, check out their color. Also, observe them in the morning just after lights on. They are usually much darker in color.
I've kept mine at an average of pH 7, but, you will soon learn that many of our fish are very hardy and adaptable. If you acclimate them to the pH of your water, they should probably adjust and do fine.
Enjoy them.
PS....check out the TFF Index and see my two posts on each one above.
SH