  We present a new method to assess the properties of transiting planet
candidates by multicolor photometry. By analyzing multicolor transit/eclipse
light curves and apparent magnitudes of the target in parallel, this method
attempts to identify the nature of the system and provide a quantitative
constraint on the properties of unresolved companion(s). We demonstrate our
method by observing the six systems hosting candidate transiting planets,
identified by the K2 mission (EPIC 206036749, EPIC 206500801, EPIC 210513446,
EPIC 211800191, EPIC 220621087, and EPIC 220696233). Applying our analysis code
to the six targets, we find that EPIC 206036749, EPIC 210513446, and EPIC
211800191 are likely to be triple-star systems including eclipsing binaries,
and EPIC 220696233 is likely a planetary system, albeit further observations
are required to confirm the nature. Additionally, we confirm that the
systematic errors in the derived system parameters arising from adopting
specific isochrone models and observing instruments (passbands) are relatively
small. While this approach alone is not powerful enough to validate or refute
planet candidates, the technique allows us to constrain the properties of
resolved/unresolved companions, and prioritize the planet candidates for
further follow-up observations (e.g., radial-velocity measurements).
