Fixed smart quote.

src/docs/asciidoc/jme3/advanced/j3m_material_files.adoc

@@ -87,7 +87,7 @@ Make sure to get the paths to the textures (.png, .jpg) and material definitions
 === Data Types
 
 All data types (except Color) are specified in com.jme3.shader.VarType.
-“Color is specified as Vector4 in J3MLoader.java.
+"`Color`" is specified as Vector4 in J3MLoader.java.
 [cols="3", options="header"]
 |===