Well, you will find a huge array of opinions about growing red plants or more specifically about keeping them red!
As far as I can work out, lots of C02 and bright light seem to be the most popular answer offered, but not necessarily the solution!
Growing and keeping them red long term would appear extremely difficult for the majority of us!
If you intend to keep your tank 'low tech' I would suggest you fill your tank with a lot more plant mass, use low light and a very small amount of ferts but trying to keep your plants red is not something I would not lose sleep over.