Over on the user submitted hackaday.io community, user marble has shared his work about using a HackRF to transmit PAL analog colored TV images with his rad1o (the rad1o is a slight variation of the HackRF One) using a GNU Radio flowgraph.
In his submission he shares a tutorial that explains the theory behind the PAL analog video standard. He explains the different components of the PAL signal, including the luma (black and white part), frame rates, and modulation. He then goes on to explain how color is encoded onto the PAL by using Quadrature Amplitude Modulation (QAM).
Finally in the files section marble also supplies us with the GNU Radio flowgraph which can be used to transmit PAL video with a HackRF.