This paper presents a novel two-layer coding framework targeting visually lossless compression of screen content video. The proposed framework employs the conventional HEVC standard for the base-layer. For the enhancement layer, a hybrid of spatial and temporal block-prediction mechanism is introduced to guarantee a small energy of the error-residual. Spatial prediction is generally chosen for dynamic areas, while temporal predictions yield better prediction for static areas in a video frame. The prediction residual is quantized based on whether a given block is static or dynamic. Run-length coding, Golomb based binarization and context-based arithmetic coding are employed to efficiently code the quantized residual and form the enhancement-layer. Performance evaluations using 4:4:4 screen content sequences show that, for visually lossless video quality, the proposed system significantly saves the bit-rate compared to the two-layer lossless HEVC framework.