figure
le=[1,2,3];
x=[0 5 15];
y=2*x;
for i =1 : length(x)
txt = ['$\alpha_1$ = ',num2str(le(1,i))];
hp1{i} = plot(x, y, '-+','LineWidth',1.5,'DisplayName',txt);
hold on
end
hold on
xlinelocs = [1 10];
hxl = xline(xlinelocs);
hp2 = patch([xlinelocs flip(xlinelocs)], [[1 1]*min(ylim) [1 1]*max(ylim)], 'b', 'FaceAlpha',0.25);
hp2.FaceColor = [1 1 1]*0.75;
grid on
set(gca,'fontweight','bold','FontSize',20)
legend([hp1{:}],'Location','best','Interpreter','latex','FontSize',16)
legend show
legend boxoff
Add or modify the patch parameters to get the desired result.
EDIT — Repositioned the legend call.
.
