Normally, a Reset sets all the chart properties (including keys and the various colour and pattern cycles) back to the initial state. You can use the ‘Reset options’ to have either keys or cycles persist through a Reset:

ch.Set 'RStyle'  'key' 

Options

keys:nokeys	Keys persist through a chart reset
cycle:nocycle	Colour, line, marker, nib and pattern cycles persist

This can be useful when you have a series of independent miniature charts which share a common key.