[Gnuplot-info] coloring points based on column value when also using hypertext labels

I have the following gnuplot data file:

1   4   foo     1
2   3   bar     2
5   8   baz     1

I have the following gnuplot command:

set terminal qt
label_text(str1) = sprintf("%s", stringcolumn(str1))
plot "gnuplot_data.txt" using 1:2:(label_text(3)) with labels hypertext
notitle
pause -1

How can I color code the points based on the value of the 4th column? I
know how to do this when not using hypertext labels, but cannot figure it
out when the 3rd field of the "using" statement is dedicated to specifying
the 3rd column for the label text.

Thanks