Jelinda, if you can plant the bulbs/plants outside now, do that. That way Mother Nature can do a lot of the work for you. Aphids seem to be a lot more of a problem in the house or the greenhouse enviornments. I would still soak the bulbs/plants in the diluted insecticide for 2-5 minutes, whether going in the house or outside. If you see any evidence of the aphids after a week or two, spray the plant(s) with the insecticide. Be sure to get the bottom of the leaves as well. You want to kill the adults BEFORE they have a chance to lay their eggs, and that ends their cycle. Neem oil and Permethrin are relatively enviornmentally safe and Malathion is very effective, but not so enviornmental-friendly.
Aphids actually come in a lot of colors - red, brown, yellow, green. Sometimes if is the species of aphid and sometimes it is the age of the aphid. Ken