Today cloud computing became an impressive solution to address the challenges in storage and process of high volume data, with low-cost, high-speed, on-demand and pay-per-use characteristics. Although rapid progression has been recorded in the area of cloud computing and its services, attaining the implementation of green clouds is still under development due to lack of research and several barriers in its implementation. Green clouds are committed to design as eco-friendly, energy efficient, max resource utilizable, low carbon emissions, long lasting and recyclable. In order to satisfy the ever growing enterprise data storage and processing needs, the cloud service providers are coming up with cutting edge technologies like Green Cloud Computing in cloud architecture design to reduce, the huge power consumption, water consumption, need of physical hardware peripherals, infrastructure and harmful carbon emissions etc. To protect our environment from cloud negative impacts, the service providers must adopt and update their cloud infrastructure towards green computing. Green computing researches widely focus on designing of efficient clouds with green characteristics like Power Management, Virtualization, High Performance Computing, Load balancing, Green data center, Reusability, Recyclability etc. As part of my research on green clouds, this paper presents an analysis report about the green cloud computing and its characteristics in detailed manner. This paper thoroughly discusses about the former green computing achievements, current trending concepts of green computing and future research challenges as well. This comprehensive green cloud analysis report helps the naïve green research fellows to learn about green cloud topics and to understand the green cloud future research challenges.