part of day 6 of AoC 2019 in unity.

SphereRotate.cs

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

public class SphereRotate : MonoBehaviour
{
    float speed = 5;
    Vector3 euls;
    // Update is called once per frame
    private void Start()
    {
        euls = transform.localEulerAngles;
        speed = 0.5f;
    }

    public void SetColor(Color c)
    {
        GetComponent<Renderer>().material.color = c;
        GetComponent<TrailRenderer>().startColor = c;
        GetComponent<TrailRenderer>().startWidth = 1f;
    }

    void Update()
    {

        euls.z += Time.deltaTime * speed;
        transform.localEulerAngles = euls;
    }
}