Generally speaking (although there are many variables in play, including the paper and exposure you use, and the developer itself), prints do not come out that colourful in fresh lith developer. As the session continues and the developer "seasons", the prints get more colourful until they begin to look muddy and/or take forever in the developer to emerge. If you want to get to the colour faster, adding old brown is a way to do it. If you prefer to have less colour, don't add old brown. Similarly, I use a paper that gets terrible pepper fogging in used developer, so I know I can only get a few good sheets in the beginning of a session, in fresh developer, with no old brown added.
Mr Rusty - putting a couple prints through the developer and then saving it for future use is not a good example of getting old brown. Have a full session with as many prints as you can put through the lith developer. When it is finished, save some of that developer (old brown) to be added to your next fresh batch to help season it. If I'm using 100ml A + 100ml B I usually add up to another 100ml of old brown. Another trick is just to let the developer oxidize (over hours) -- as it's exposed to air it will continue to change it's properties, much like having a series of prints go through it.