In reply to Andreas Lindberg.

If you want one tick mark to be different than the others, I think you would have to use an annotation data set. When I want to highlight a special value, I use a REFLINE statement and label it so that it looks like an extra tick mark. For example, see https://blogs.sas.com/content/iml/2022/08/24/stagger-labels-axis.html
The following graph shows this technique:

proc sgplot data=sashelp.class;
scatter x=Height y=Weight;
refline 125 / axis=y label="125" labelpos=min labelattrs=(color=red)
transparency=0.75;
xaxis grid;
yaxis grid;
run;