Draw a colorpicker

public class BuildingTexture : MonoBehaviour {
    private float colorStep = 3/128; //   1/(256/6) this*42 is nearly 1
    private Color tempColor = new Color (1,0,0,1);
    public Texture2D tex = new Texture2D (256, 256);

    // Use this for initialization
    void Start () {
        renderer.material.mainTexture = tex;
        for (int x=0; x<=42; x++) { //42 steps in each for loops
            tempColor.g = tempColor.g+colorStep;
            drawLine(x,tempColor);
        }
        for (int x=43; x<=84; x++) {
            tempColor.r = tempColor.r-colorStep;
            drawLine(x,tempColor);
        }
        for (int x=85; x<=127; x++) {
            tempColor.b = tempColor.b+colorStep;
            drawLine(x,tempColor);
        }
        for (int x=128; x<=170; x++) {
            tempColor.g = tempColor.g-colorStep;
            drawLine(x,tempColor);
        }
        for (int x=171; x<=212; x++) {
            tempColor.r = tempColor.r+colorStep;
            drawLine(x,tempColor);
        }
        for (int x=213; x<=256; x++) {
            tempColor.b = tempColor.b-colorStep;
            drawLine(x,tempColor);
        }

        tex.Apply();
        Debug.Log (tex);
    }

    void drawLine(int x, Color tempColor){
        Debug.Log(tempColor);
        for (int y=0; y<256; y++) {
            tex.SetPixel (x, y, tempColor);
        }
    }

    // Update is called once per frame
    void Update () {

    }
}