using System;
using System.Linq;
using System.Text.RegularExpressions;

public class Test
{
	public static void Main()
	{
		var text="red 1 green 3 blue";
		Console.WriteLine(string.Join(";", Regex.Split(text, @"red|green|blue")));
		Console.WriteLine(string.Join(";", Regex.Split(text, @"red|green|blue").Where(x => !string.IsNullOrEmpty(x))));
	}
}