Why doesn't the color vector work here?

I'm plotting a math function with a customized grid, but the color of the latter is black, whereas I've defined it as grey. Why does this happen and how can I fix it?

% Gráfica de Mecánica de Fluidos
function []=a3(gamma)
figure(1), close(1),figure(1)
% Llamo quo a A(s)/Amin
M=0:0.01:6;
num=(1+(gamma-1)/2)^(-(gamma+1)/(2*(gamma-1))); 
den=M.*(1+(gamma-1).*M.^2/2).^(-(gamma+1)/(2*(gamma-1))); 
quo=num./den; 
g_x=0:1/4:6; % grid 
g_y=0:1:60;  % grid 
grey=[1 1 1]*0.4; % grid colour 
for k=1:length(g_x)
    plot([g_x(k), g_x(k)], [g_y(1), g_y(end)],'color',grey)
    hold on 
end 
for k=1:length(g_y)
    plot([g_x(1), g_x(end)], [g_y(k), g_y(k)],'color',grey)
    hold on 
end
plot(M,quo,'r')
title('Cociente de áreas frente al Mach')
xlabel('M(s)')
ylabel('A(s)/Amin')

%

Answer 1

[Ced]

Try

grey=[1 1 1]*0.8; % grid colour

[Ricardo Boza Villar]

I don't know why but I kept reducing that coefficient on and on instead of increasing it. Thank you :)

Answer 2

[Image Analyst]

Looks gray to me. The grid lines are definitely not as dark as the black title. If you want you could try line() instead of plot(). With one pixel wide lines, you might have an aliasing problem so the colors might not be what you expect.

[Ricardo Boza Villar]

I'm a beginner, but I'll look into it.

By the way, there might be some expressions I write which sound odd, but English isn't my native tongue, so... sorry for that!

Answer 3

[Ricardo Boza Villar]

Thank you both for your answers. The problem is solved, but I'd like to ask something else. Is it me or when I have several parallel lines it looks as if there were some lines which are very well defined (as if they met a line of pixels), and some other lines which aren't (they don't have as good definition as the others). What is responsible for this, the archive format or my computer screen? And why?

[Image Analyst]

It could be due to anti-aliasing. What if grid line #1 was supposed to be at line #101 on your monitor, and grid line #2 was supposed to be at line #143.5 on your monitor. But there is no line #143.5, so line 143 gets half a line and line 144 gets half a line, which means the grid line is split over two monitor lines and each line is half as dark (twice as bright), so the line looks fainter instead of being a nice solid dark line like the line that landed exactly at line #101.

[Ricardo Boza Villar]

Thank you!