Can I create a color image with a GAN consisting of only FC layers?
I understand that in order to create a color image, three channel information of input data must be maintained inside the network. However, data must be flattened to pass through the linear layer. If so, can GAN consisting of only FC layer generate only black and white images?

Your fully connected network can generate whatever you want. Even three channel outputs. However, the question is: does it make sense to do so? Flattened your input will inherently lose all kinds of spatial and feature consistency that is naturally available when represented as an RGB map.
Remember that an RGB image can be thought of as 3-element features describing each spatial location of a 2D image. In other words, each of the three channels gives additional information about a given pixel, considering these channels as separate entities is a loss of information.
