How can I fill empty and closed areas with the flood fill algorithm?

I want the floor to fill with the color I choose when the object creates any shape with space in the middle. It should automatically fill the gaps between the lines\boxes. How can I do that?

This is my flood fill code:

 public class FloodFill : MonoBehaviour
 {
     [SerializeField] private float fillDelay = 0.01f;
     private GridManager gridManager;
     void Start()
     {
         gridManager = this.GetComponent<GridManager>();
     }
 
     public IEnumerator Flood(int x, int y, Color oldColor, Color newColor)
     {
         WaitForSeconds wait = new WaitForSeconds(fillDelay);
         if (x >= 0 && x < gridManager.xSize && y >= 0 && y < gridManager.ySize)
         {
             yield return wait;
             if (gridManager.grid[x, y].GetComponent<SpriteRenderer>().color == oldColor)
             {
                 gridManager.grid[x, y].GetComponent<SpriteRenderer>().color = newColor;
                 StartCoroutine(Flood(x + 1, y, oldColor, newColor));
                 StartCoroutine(Flood(x - 1, y, oldColor, newColor));
                 StartCoroutine(Flood(x, y + 1, oldColor, newColor));
                 StartCoroutine(Flood(x, y - 1, oldColor, newColor));
             }
         }
     }
 }

and this is fill for just borders:

 if (hit.collider != null)
         {
             mov = false;
             if (Mathf.RoundToInt(this.transform.position.x) >= gridManager.xSize / 2 && Mathf.RoundToInt(this.transform.position.y) >= gridManager.ySize / 2)
             {
                 if (currentDirection == up)
                 {
                     StartCoroutine(floodFill.Flood(Mathf.RoundToInt(this.transform.position.x + 1), Mathf.RoundToInt(this.transform.position.y), Color.white, Color.green));
                 }
 
                 if (currentDirection == right)
                 {
                     StartCoroutine(floodFill.Flood(Mathf.RoundToInt(this.transform.position.x), Mathf.RoundToInt(this.transform.position.y + 1), Color.white, Color.green));
                 }
             }
 
             if (Mathf.RoundToInt(this.transform.position.x) <= gridManager.xSize / 2 && Mathf.RoundToInt(this.transform.position.y) <= gridManager.ySize / 2)
             {
                 if (currentDirection == down)
                 {
                     StartCoroutine(floodFill.Flood(Mathf.RoundToInt(this.transform.position.x - 1), Mathf.RoundToInt(this.transform.position.y), Color.white, Color.green));
                 }
 
                 if (currentDirection == left)
                 {
                     StartCoroutine(floodFill.Flood(Mathf.RoundToInt(this.transform.position.x), Mathf.RoundToInt(this.transform.position.y - 1), Color.white, Color.green));
                 }
             }
 
             if (Mathf.RoundToInt(this.transform.position.x) < gridManager.xSize / 2 && Mathf.RoundToInt(this.transform.position.y) > gridManager.ySize / 2)
             {
                 if (currentDirection == up)
                 {
                     StartCoroutine(floodFill.Flood(Mathf.RoundToInt(this.transform.position.x - 1), Mathf.RoundToInt(this.transform.position.y), Color.white, Color.green));
                 }
 
                 if (currentDirection == left)
                 {
                     StartCoroutine(floodFill.Flood(Mathf.RoundToInt(this.transform.position.x), Mathf.RoundToInt(this.transform.position.y + 1), Color.white, Color.green));
                 }
             }
 
             if (Mathf.RoundToInt(this.transform.position.x) > gridManager.xSize / 2 && Mathf.RoundToInt(this.transform.position.y) < gridManager.ySize / 2)
             {
                 if (currentDirection == down)
                 {
                     StartCoroutine(floodFill.Flood(Mathf.RoundToInt(this.transform.position.x - 1), Mathf.RoundToInt(this.transform.position.y), Color.white, Color.green));
                 }
 
                 if (currentDirection == right)
                 {
                     StartCoroutine(floodFill.Flood(Mathf.RoundToInt(this.transform.position.x), Mathf.RoundToInt(this.transform.position.y - 1), Color.white, Color.green));
                 }
             }
         }
         else
         {
             mov = true;
         }