My recipe for coralline growth:
Water Chemistry: Make sure you are keeping your water at NSW levels. Many believe it helps to have magnesium (Mg) a little higher, between 1300-1500 meq/L range, Potassium (K) should be at NSW range, 399 ppm (390-410 ppm). Salinity 35 ppt. Nutrients LOW, Phosphate (PO4) <0.03 ppm, Nitrate (NO3) <0.05 ppm.
Lighting: Most any lighting source will work as long as it is in the right spectrum. MH, T5, LED, Plasma, etc. need to be more blue spectrum. Warm light, <5000K grows green pest algae well. Cool or actinic light, 10,000K - 20,000K grows coralline algae, as it does corals. If you do not have enough blue spectrum in your overall light source you will find it difficult if not impossible to grow coralline.
Flow: Like stony corals, coralline algae needs considerable flow to bring nutrients to it, and waste from it. Your flow does not need to be extremely high, but good flow is what it likes. The flow also helps distribute spores from the coralline to other places in the tank, thus spreading it.
Seeding: I believe ReefDVM's did a video on coralline plates purchased from IPSF, look for it in the video gallery section. By placing the plates or any other material with coralline algae on it in a good flow area, in time, the coralline will grow and spore. Another method is to scrape existing coralline off a piece of rock or plate into the display tank. I find this method to be a less effective way of introducing coralline to a tank. You want the spores themselves, as they are small and can better attach themselves to a surface. This takes time as the coralline needs to mature and spore on it's own in cycles.
There is no rushing the process of coralline algae growth, it will happen in time if the above conditions are met and kept consistent. The more coralline you have in your tank, the more spores will be introduced into the water column on a continual basis. This can lead to epidemic proportions for some people who actually find coralline algae to be a pest organism that is difficult to remove from tank equipment.
Different colours of coralline exist in nature, from a dark purple to a light pink to green. Seeding different colours into the tank gives you a mosaic look to your rock, seeding only one colour gives you a monotone look to your rock. Myth (busted): Purple-Up, a product marketed by CaribSea intended to produce coralline algae in your tank is nothing more than a CaCO3 (ALK) with aragonite powder and Mg, it contains no coralline spores. Basically snake oil.