Changing color of sprite not working?

Hello, I am instantiating a sprite into my game, and at first I want to give it a random color, but as the next sprite spawns I want the color to change a tiny amount. I have a small bit of code that chooses a random color nicely, but when I try changing the color on the next sprite, it goes back to the original sprite color. Any help is appreciated thanks!

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

public class spawner : MonoBehaviour {

	public GameObject circle;
	public float shrinkRate;
	public static bool canSpawn = true; 
	private Color customColor;

	// Use this for initialization
	void Start () {
		chooseRandomColor ();
	}
	
	// Update is called once per frame
	void Update () {
		if (canSpawn == true) {
			canSpawn = false;
			var circleVector = new Vector3 (0, 0, 0);
			var circleInstance = Instantiate (circle, circleVector, Quaternion.Euler(0, 0, Random.Range(0.0f, 360.0f)));
			customColor.r = customColor.r + 1f; 
			customColor.g = customColor.g + 1f;
			customColor.b = customColor.b + 1f;
			circleInstance.GetComponent<SpriteRenderer> ().color = customColor;
		}
	}

	void chooseRandomColor () {
		customColor = new Color (Random.value, Random.value, Random.value);
	}
}

Color’s rgb values are in range 0 to 1, so customColor.r += 1f will cause the r value exceed 1, in that case the value will be clamped to 1, which will result a white tint color and the sprite’s color won’t change at all.

I think what you want is customColor.r += 0.1f (10%)