1. A method of video coding for a block of depth data or texture data coded in SSM (Single Sample Mode), the method comprising: receiving input data associated with a current block, wherein the current block corresponds to a depth block or a texture block; constructing a sample candidate list comprising one or more single color candidates corresponding to one or more representative samples of one or more previous SSM-coded blocks, or one or more palette color candidates corresponding to one or more previously used colors in one or more previous palettes of a plurality of colors associated with one or more palette-coded blocks, or both of said one or more single color candidates and said one or more palette color candidates; determining a single selected sample candidate from the sample candidate list; and encoding the current block by representing all samples in the current block by said single selected sample candidate at an encoder side, or decoding the current block by using said single selected sample candidate as a reconstructed value for all samples in the current block at a decoder side, wherein the sample candidate list further comprises one or more spatial candidates from previously reconstructed neighboring spatial samples of the current block, one or more temporal candidates from previously reconstructed temporal sample in or around a temporally collocated block of the current block, and said one or more single color candidates, and wherein said single selected sample candidate is selected based on a priority order corresponding to one of: (i) candidate types associated with said one or more spatial candidates, said one or more temporal candidates, and said one or more single color candidates, and (ii) interleaving among said one or more spatial candidates, said one or more temporal candidates, and said one or more single color candidates.