I haven't grown the coloured ones but I've experience with the common white one and Arum dracunculus. So, in assuming that the coloured ones are similar to the white one in requirements, I'll say this. They'd grow much better in the garden than in the pots. They don't like to dry out too much. They don't need any fertilizer and I'd avoid giving them any. They'll gradually increase in clump size and can be difficult to eradicate (every little piece of rhizome left in the ground will grow) if you decide you don't like them any more. They don't like frost. They'll get quite straggly after their flowering season and sometimes the whole plant will fall over from the base. If tired of this look, although not ideal for the plant, you can chop it back to just above the soil and it'll grow again. It goes dormant in winter (i.e. no plant above ground). You could plant yours out while in flower - they'll probably droop for awhile but just give them a good watering. Hopefully someone who grows the coloured ones will confirm or give more specific advice. They're poisonous so no eating them...