  We initiate the study of extended bicolorings of Steiner triple systems (STS)
which start with a $k$-bicoloring of an STS($v$) and end up with a
$k$-bicoloring of an STS($2v+1$) obtained by a doubling construction, using
only the original colors used in coloring the subsystem STS($v$). By producing
many such extended bicolorings, we obtain several infinite classes of orders
for which there exist STSs with different lower and upper chromatic number.
