This is a modern cushion cover made from good old granny squares. The squares are knit from corner to corner increasing and then decreasing to get the square shape and the colour is changed half way across the square. The back is made by picking up stitches along the bottom after the squares are joined and knitted until it is the same size as the back. Stitches are then picked up along the top and a flap knitted with buttonholes to fasten it. The back could be the same as the front if desired. I was just using yarn left from another project. There is a chart to show you where to place the squares.
Be as bold or as subtle as you like with the colours you choose!