The bi-modality in the distribution of galaxies usually obtained from color-color or color-mass diagrams has been studied to show the difference between the "blue cloud" and "red sequence" galaxies and to define the Green Valley (GV) region. However, there are still many open questions regarding the importance of the green valley for understanding the morphological transformation and evolution of galaxies, how galaxies change from late-type to early-type and the role of AGN in galaxy formation and evolution scenario especially in the green valley. The study focused on studying in more details different green valley selection criteria used in previous works as well as differences between them and how the initial selection of green valley galaxies could affect the final results and conclusions. The main findings were that by selecting the GV galaxies based on UV or optical data we are selecting different types of galaxies in terms of their stellar masses, luminosities, SFRs and morphological classification where the stellar mass was higher in GV samples selected in UV than the GV samples selected in optical while the star formation rate as well as the specific star formation rate were higher in GV samples selected in optical than the GV samples selected in UV, the difference were more significant for color criteria. The morphological classification of the GV selected samples have been obtained and galaxies were classified into spirals, ellipticals and uncertain galaxies and the results suggested that most of the objects in the GV are spirals or have an uncertain visual morphology.