Cache materials into List (or array) and restore from cached List?

Hey guys, I have a character which consists of several game objects each with different material. When my character is hit I want to flash all it's pieces with white color. And after short time return to materials there were before

I grab all renderers and materials into arrays:

 void Start()
     {
         renderers = GetComponentsInChildren<Renderer>().ToList().FindAll(el => !((el is ParticleSystemRenderer)||(el is TrailRenderer) )).ToArray();
         materials = GetComponentsInChildren<Material>().ToList().FindAll(el => !((el is ParticleSystemRenderer)||(el is TrailRenderer) )).ToArray();
     }

To replace materials with dedicated Flash material (plain white color)

 foreach (var el in renderers)
 {
     if (flashMaterial != null)
     rend.material = flashMaterial;
 }    

so the question is: How can I restore original materials after such replacement?