Why does the Color of this Unity lineRenderer never change the line color?

Hi,

My Unity C# game  needs just a few more graphical abilities.

I can generate lines, as needed, in code as such  - this should show the key uses :

(towerNumber is an instance variable.)

......

  line = (new GameObject("line"+ TowerNumber)).AddComponent<LineRenderer>();

        line.startWidth = (float) 0.3;
        line.endWidth = (float)0.3;


        line.startColor = Color.yellow;
        line.endColor = Color.blue;
            


        Vector3[] positions = new Vector3[2];
        positions[0] = new Vector3(0, 0, 0);
        positions[1] = new Vector3(TowerNumber * 2, -1, 0);


        line.SetPositions(positions);

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If I change the start and end Widths in code, the line changes width,
but the color never changes (for start or end color) and I can't see why? It is always magenta - does that mean ERROR?
Thanks