Adding Placeholders on Specific Increments Within a Graph

My project instructions indicate that the red markers must appear on increments of 2mm, so 2,4,6,8,10 (mm). My current script generates the red square on every increment. How can I modify it to only appear on increments of 2mm?

d=[1,2,3,4,5,6,7,8,9,10];

YieldStrength=[21600,1.8788e+04,1.7543e+04,16800,1.6293e+04,1.5919e+04,1.5628e+04,1.5394e+04,15200,1.5036e+04];

x=d;

y=YieldStrength;

plot(x,y,'--bs','linewidth',0.5,'markersize',5,'markeredgecolor','r','markerfacecolor','r');

xlabel('Diameter (mm)')

ylabel('Yield Strength (psi)')

title('Yield Strength vs. Diameter')