This is a great question and something at Columnrads that we get asked quite a lot. We think it is fantastic that customers are trying to liven up a rad. Before yes rads where all white and old ones are generally yellowish, dirty white now there is no limits to what you can produce. The problem is that unless you have a designated spray booth with all the modern paint technology you are just not going to be able to produce a great finish.
There are different reasons for painting and people paint different types of radiators in different ways. Normal rads, panel or convectors are generally finished in a high gloss RAL 9016 as standard and can be painted due to matching a room colour, dents or scratches and general discolouration. This is fine as they are a fairly inexpensive item and yes they do not often fit in. Column rads and towel rails on the other hand are a totally different ball game and in our opinion need to be professionally painted. There is the also the really popular raw metal finish that is actually a clear powder coat on the raw steel. This is a finish that cannot be re-created in the home and is something that the factory has perfected over years of trailing and laboratory inspection. There is also the stocked Express and Hammered Gold finish that really cannot be replicated outside of the factory.
To paint a radiator in the home is generally done by a metal based paint but these are totally different to a spray on powder coat and you cannot achieve the high quality finish. So if you are thinking about either column or towel rads and you want a specific finish please get a quote from Columnrads because you never know you might actually be surprised how cheap they actually are.