A method for video processing is provided to comprise: dividing a video block of a first color component to obtain a first set sub-blocks of the first color component; dividing a corresponding video block of a second color component to obtain a second set of sub-blocks of a second color component; deriving one or more motion vectors of the first set of sub-blocks based on one or more motion vectors of the second set of sub-blocks; and performing, based on the one or more motion vectors of the first set and second set of sub-blocks, a conversion between the video block and a coded representation of the video.