"Marble"
  Dip
  I have seen a few crown dips over the past several years that
  were really unique in that they had a marbling effect where there
  is a base color and a contrasting color giving the dip a veined
  appearance (see photo of finished arrow). At the PBS arrow building
  contest in Seattle in 1998 there were several arrows with this
  kind of dip.
  I was curious as to how it was done and set out to find out.
  Actually, I think it was Brian Cole who talked to one of the
  arrow artists and discovered the method to make this unique looking
  crown dip and it really isnt hard to do.
  I start by putting on two coats of clear finish and a base
  coat of white. Make sure that you have rubbed out the finish
  with steel wool after each coat. Next, get a short dip tube or
  you can even use a glass vase or jar to make your marble dip.
  The secret is to float the paint on water and then dip through
  the paint and water. The paint will float on the top of the water.
  I am using a fast drying enamel called "Odds and Ends".
  The paint needs to be thinned quite a bit until you get a real
  runny consistency. If the paint is too thick you will end up
  with globs of paint and air bubbles. Pour in your base color
  first. In this example I am using yellow. Then slowly pour in
  your contrasting paint (or paints if youre using more than
  one color). As you are pouring it in let it come out in a small
  stream and swirl it all around the base color. Once you have
  done this mix it up a little, but not enough to totally blend
  the two colors. Just take a tooth pick and swirl it around a
  little. (See photo for mixed paint). Now you can dip your shaft
  through the paint and water. You may have to dump this mix out
  after a couple of shafts if the paint blends together and you
  are no longer getting the marble effect. In the example shown
  I used a combination of yellow and blue and ended up with a yellow/green
  looking color.
  Experiment with different color combinations and use your
  imagination for something that is really unique.