Devices, systems and methods for video processing are described. An example method for video processing includes performing a conversion between a video comprising luma blocks and corresponding chroma blocks and a bitstream representation of the video according to a rule that specifies that, for a case that a current luma block is coded using a palette coding mode and a corresponding current chroma block coded with a derived mode, the current luma block is treated as having a default intra prediction mode and the current chroma block is coded with the default intra prediction mode.