How to reverse COLORMAP?

Hi, Matlab users

I am going to plot a graph using function Colormap and Colorbar.
Suppose I have a square in 2D space,i.e.,-1 <x <1 and
-1<y<1, where 100 points are evenly distributed. That is, 10
points along one side.

Now I have assigned scalar values to these 100 points from 0 to 1.
And I want to plot these values along the above square such that the
large value corresponds to color Black and small value corresponds to
color White.

However, when I tried to plot it using Colormap(gray) and Colorbar,
the output figure is plotted with black corresponding to smallest
In order to make the plot look better, I need to reverse the color of
my graph.
So how to control or change the setting of function Colormap?