1. A method of coding a block of video data using palette coding for a video coding system, the method comprising: receiving input data associated with a current block, wherein pixel values of the current block correspond to multiple color components; if a previous block is valid: receiving first information related to a previous palette set corresponding to one or more previous palettes, one previous triplet-palette, or both associated with the previous block; receiving second information related to a previous palette predictor set corresponding to one or more previous palette predictors, one previous triplet-palette predictor, or both associated with the previous block; deriving a current palette predictor set corresponding to one or more current palette predictors, one current triplet-palette predictor, or both associated with the current block based on the previous palette set and the previous palette predictor set by including at least one unused color or at least one unused triplet of the previous palette predictor set in the current palette predictor set when said at least one unused color or said at least one unused triplet of the previous palette predictor set in the current palette predictor set exists; deriving a current palette set corresponding to one or more current palettes, one current triplet-palette, or both associated with the current block from the current palette predictor set; and applying palette encoding or decoding to the current block according to the current palette set.