Task scheduling is of paramount importance in a desktop grid environment. Earlier works in the area focused on issues such as: meeting task deadlines, minimizing make-span, monitoring and checkpointing for progress, malicious or erroneous peer discovery and fault tolerance using task replication. More recently energy consumption has been studied from the standpoint of judiciously replicating and assigning tasks to the more power efficient peers. In this paper we tackle another aspect of power efficiency with regards to scheduling, namely greenness of the consumed energy. We give a formulation as a multi-objective optimization problem and propose heuristics to solve it. All the heuristics are evaluated via simulation experiments and conclusions on their merits are drawn.