Sprite.Create alpha

Can anybody tell me why created sprites are translucent?

void Start ()
    {
        Texture2D texture = new Texture2D(32, 16);
        spriteRenderer.sprite = Sprite.Create(texture, new Rect(0.0f, 0.0f, texture.width, texture.height), new Vector2(0.5f, 0.5f), 4.0f);
    }

White sprite has a higher render order and has an alpha of 1 yet we can see through it?

This is the default way textures are created - see the docs.

As the docs state

Usually you will want to set the
colors of the texture after creating
it, using SetPixel, SetPixels and
Apply functions

Check out this modification to your script

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

public class SpriteManager : MonoBehaviour
{
    public SpriteRenderer spriteRenderer;
    public Color defaultColor = Color.white;
	void Start ()
    {
        if (spriteRenderer != null)
        {
            Texture2D texture = new Texture2D(32, 16);
            List<Color> cols = new List<Color>();
            for (int i = 0; i < (32 * 16); i ++)
            {
                cols.Add(defaultColor);
            }
            texture.SetPixels(cols.ToArray());
            texture.Apply();
            spriteRenderer.sprite = Sprite.Create(texture, new Rect(0.0f, 0.0f, texture.width, texture.height), new Vector2(0.5f, 0.5f), 4.0f);
        }
	}
}