One approach —
plot(xlim, [0 0]+min(ylim), 'g')
xtv = compose('%.0f',xt);
Ax.XAxis.Visible = 'off';
text(xt,zeros(size(xt)), xtv, 'Color','r', 'Horiz','center', 'Vert','top')
This turns the x-axis visibility off, draws the x-axis in green, and plots the tick values in red. The ticks themselves are also now invisible, they would have to be added back with a plot call if desired.