src/main/java/com/basistech/tclre/Arc.java
boolean colored() {
        return type == Compiler.PLAIN || type == Compiler.AHEAD || type == Compiler.BEHIND;
    }
boolean colored() {
        return type == Compiler.PLAIN || type == Compiler.AHEAD || type == Compiler.BEHIND;
    }
is an arc colored, and hence on a color chain?