robust column reference

[#1]

After a few minutes coding with JSL, users wonder about strange objects like :sex in 

dt = Open( "$SAMPLE_DATA/Big Class.jmp" );

x = :sex

Expert users have some experience with such column references and use them all the time.
But what is :sex ? Is  dt:sex  more robust? Where do I find a documentation ?

Let's collect and share some insights.

my 5 cents:

[#2]

Take home message:

With the learning from 

myList2 = Eval List({Name Expr(As column(:name)),Name Expr(As column(:sex)),Name Expr(As column(:age))});

we can convert any list provided by JMP into a robust list of columns via

ColNames = dt << get column names;
colList = Transform Each({col}, ColNames, Name Expr(As Column (col)));