No it's red or purple. To get some you may need to deliberately introduce some to your tank. What I did is got to my LFS, get a small rock with many colonies of purple algae and put it in my tank. You may want to acclimate it first so the algae doesn't die. It has worked for me so I hope it can work for you. After a week or two you can try to scrape of some algae and put the scrapings in the water.
It comes in green as well.. to know its coraline .. try to scrap it with your finger if it doesn't come off easily its coraline .. it doesn't start green comes in a verity of colors green pink purple and some shades of red/ marroon... it forms by extra calcium in the collum.. best way is to get some live rock from ur lfs that has a good amount on it and watch it spread.
yeah coralline aglae is aglae, it consmes calcium, magniusium and srontium from the water, but having said that it also prevents the spread of many other pain in the butt algaes and it is still rather perty looking
mine went in stages first i had brown diatoms then i had green film algae that was always covering my glass now i have an explosion of coralline algae almost overnight it started covering my intake and back glass i wonder though why doesnt it really ever cover the front glass as much as the back?