Convert a label table to the format the writer expects.
cifti.label.table.for.writing(label_table)a data.frame with the columns 'key', 'red', 'green', 'blue', 'alpha' and
'label', or NULL.
a data.frame, see cifti.axis.labels, the colortable of
an fs.annot instance, or NULL. The column names are matched case-insensitively, so
the label table that read.fs.parcellation.cifti returns (with the columns
'Key', 'Red', 'Green', 'Blue', 'Alpha' and 'Label') can be passed directly. The
colortable of a FreeSurfer annotation stores the colors in the range 0 to 255, and it
is converted here.