If beer 1 was very high alcohol, you might not have a lot of viable yeast, but going from a 6% beer to a 4% beer shouldn't cause any problems. The color issue is because you might have some flavors/colors sneak into the new beer. Since we're talking about a very small amount of fluid that's been washed, you shouldn't have any serious issues. I'm of the opinion that what settled out once will settle out again. If you make a starter, you'll ensure healthy yeast and dilute out some of those other compounds you wanted to get rid of.