Another factor in the production of large pitchers is light levels.
In full sun, Cephalotus will pitcher quite happily and these pitchers will be well coloured in reds and purples, but, they will be smaller compared to those produced in shade although these normally will remain green. The way round this is to grow them initially in shade (approx 50% shade cloth) until the crop of pitchers are full size and to slowly introduce them to more light, to bring out the red/purple colouration.
I tend to grow my plants in permanent semi shade although I do let half my plants have a sunbathe as it seems to produce 'harder' plants that seem less susceptible to winter moulds.
In the last 4 years I've found that keeping the plant in shady conditions during the summer months combined with full sun conditions during the autumn and winter months produces the ideal conditions for large size pichers and well coloured pitchers with the additional benefit of keeping down mould growth.
Those plants that I grow under artificial light in a grow chamber are lit by no more than two 48 inch fluorescent tubes (shop fitting types are perfect) about 12 inches from the plants. This produces some colouration to the pitchers as well as producing decent sized pitchers. During winter 10-12 hours of light is plenty - raise this to 14-16 hours during the growing season.
If you just want to grow Cephalotus on a window cill the light levels will be OK - just don't let it get too hot - see Cultivation -Temperature