Copyright does not protect styles
In a recent decision of the Full Federal Court, the Court reaffirmed the fundamental legal principle that copyright does not protect ideas and concepts but only the particular form in which they are expressed.[2] The effect of this principle is that you cannot copyright a style or technique. Copyright only protects you from someone else reproducing one of your actual artworks not from someone else coming up with their own work in the same style.
In the recent Full Federal Court case one visual artist had produced artworks which were in many ways similar to those of another, better established artist. The first artist had used the same style of painting and similar colours, techniques and subject matter to the second artist. The Court found that this was not, of itself, enough to amount to copyright infringement.
http://www.artslaw.com.au/articles/entry/i-like-your-style-part-i-copyright-infringement-or-not/