In general, this disclosure describes techniques for coding video blocks using a color-space conversion process. A video coder, such as a video encoder or a video decoder, may determine whether to use color-space conversion for a coding unit and set a value of a syntax element of the coding unit to indicate the use of color-space conversion. The video coder may apply a color-space transform process in encoding the coding unit. The video coder may decode the syntax element of the coding unit. The video coder may determine whether a value of the syntax element indicates that the coding unit was encoded using color-space conversion. The video coder may apply a color-space inverse transform process in decoding the coding unit in response to determining that the syntax element indicates that the coding unit was coded using color-space conversion.