aphids=greenfly does come in range of colours..depending of the 'variety' of the aphid..there is some very plant specific species eg..rose aphids, bean etc.
If there is not that many about you could just 'run' your finger over them and squash majority of them..if you don't use any chemical you are able to keep the numbers down so no damage occur to the plants and the preadator eg. ladybirds etc. will soon come along and help with the job.. ;)
Or..you could mix some soapy water..made with washing up liquid and spray some of that..and after few days maybe blast some plain water to 'rinse' them down.
Once the cold weather sets in...aphids slowdown and what ever remains..if...you can then wash off from picked leaves if needs to be.