Create an 100x20 uint8 array. Assign 0 to the locations that are not the two max. Assign 1 to the locations that are the second maximas. Assign 2 to the locations that are the maximas.
Now image() the array, and invoke a colormap() of three colors, with the first row indicating the color for the entries that are not maxima, with the second row indicating the color for the entries that are the second maxima, and with the third row indicating the color for the entries that are the main maxima.
When you do this, pay attention to whether you want the high row numbers to appear at the top of the screen (YDir 'reverse' is default for image()) or at the bottom of the screen (YDir 'normal')
In the special case where you do not want to distinguish between maxima and second maxima, then you can create a logical array that is true for the maxima and second maxima. Then spy() the array.