I would use my rulers and ruler foot to quilt 1 straight line along the V of the coloured triangle, do another V halfway down, and then straight stitch the top of the triangle and on to the next one. I would then repeat it in the white triangles. If you don’t have a ruler foot and ruler, you can still do it but you would need to go around the quilt 3 times. There is nothing wrong with just SITD the seam lines if you are a beginner.