Plot Options
The plot command has an optional third argument that can be used to specify the line color and style. Examples:
plot(v, fv, �g�); % green line
plot(v, fv, �b:�); % blue dotted line
plot(v, fv, �r+�); % red crosses
plot(v, fv, �c--�); % cyan dashed line
Use help plot to find other possibilities