ShiftColorToViewExtension.cs

using System;
using System.Threading.Tasks;
using Xamarin.Forms;

public static class ViewExtensions
{
	public static void ShiftColorTo (this VisualElement view, Color sourceColor, Color targetColor, Action<Color> setter, uint length = 250, Easing easing = null)
	{
		view.Animate ("ShiftColorTo",
			x => 
			{
				var red = sourceColor.R + (x * (targetColor.R - sourceColor.R));
				var green = sourceColor.G + (x * (targetColor.G - sourceColor.G));
				var blue = sourceColor.B + (x * (targetColor.B - sourceColor.B));
				var alpha = sourceColor.A + (x * (targetColor.A - sourceColor.A));

				setter(Color.FromRgba(red, green, blue, alpha));
			},
			length: length,
			easing: easing);
	}
}