Question: How do I plot each point of a parametrized curve with a different color in PlotPositionVector using curveoptions?

I am using Maple 18 to plot iterates of a discrete map.  A vector R1 is parametrized by the label b that runs from 0 - 2*Pi.  The following initial iterate gives me a blue circle:  

>a := 1.0
>q := a*cos(b)
>p := a*sin(b)
>R1 := PositionVector([q, p], cartesian[x, y])
>PlotPositionVector(R1, b = 0 .. 2*Pi);

Is there a way for me to assign a gradient colorscheme to each point of the circle, using b as parameter from 0 - 2*Pi? I have tried using the following, which does not give an error message, but it also just gives me a blue circle:

>PlotPositionVector(R1, b = 0 .. 2*Pi, curveoptions = [colorscheme = ["valuesplit"]]);

I am not sure how to use the vector and mapping options in the command >plotcommand(plotargs, colorscheme=["valuesplit", V, mapping]) to obtain the color gradient along the circle.