  Molecular absorption bands are estimators of stellar activity and spot cycles
on magnetically active stars. We have previously introduced a new color index
that compare absorption strength of the titanium oxide (TiO) at 567 nm with
nearby continuum. In this paper we implement this index to measure long-term
activity variations and the statistical properties of the index in a sample of
302 solar-type stars from the HARPS planet search program. The results indicate
a pattern of change in star's activity, covers a range of periods from 2 years
up to 17 years.
