He begs Nick Carraway (his neighbor) to call up daisy so he could meet with her at Nick's house. Nick calls her and she says yes. While they wait for daisy to come for tea later on he brings butlers and such and they organize flowers. The whole living room area is full of flower arrangements. He does all this to remember old times and try to get daisy back but remember daisy is married. Thas where the green light comes in and is explained.
