First a recommendation:
don't use the plot function - it is only meant for compatibility with Matlab.
Use one of the plot2d functions.
As my sources, I point you to the online documentation of the latest version of Scilab as of today (5.3.3). You can choose the markers among those available in the section 'mark_style' in this page:
http://help.scilab.org/docs/5.3.3/en_US/polyline_properties.html
The star is the mark_style 14, the filled circle is 0, the circumference is 9.
The filling and the contour are given by the mark_foreground and mark_background properties.
So, test the following in Scilab:
x=[7;8;9;10];
y=[1;2;3;4];
plot2d(x,y,...
rect=[min(x)-.5,min(y)-.5,...
max(x)+.5,max(y)+.5],...
style=-14)
a=gca();
e=gce();
a.title.font_size=4;
xtitle('Plot2D example of a simple plot',...
'$\scalebox{2}{\boldsymbol{x}}$',...
'$\scalebox{2}{\boldsymbol{y = x - 6}}$');
l=legend(e,['y(x)'],4,%t, pos="lower_caption");
poly1= a.children(2).children(1);
poly1.mark_mode="on";
poly1.mark_style=14;
poly1.mark_size_unit = "point";
poly1.mark_size=12;
poly1.mark_foreground = color("blue");
poly1.mark_background = color("green");