u-band light curve, u − r light curve, and r vs. u − r variations for four different objects in NGC 2264: a) CSIMon-000877, a representative of the stochastic accretion bursters class; b) CSIMon-001247, a prototypical WTTS; c) CSIMon-000660, an AA Tau-like CTTS; d) CSIMon-000433, a UX Ori-like object. Light curves report all flux measurements obtained from the monitoring campaign for a better overview of the variability pattern, but only observing sequences obtained in photometric conditions (see Table 1) are retained for the color analysis. Each point in the r vs. u − r diagram for a given object corresponds to the average u − r color and r-band magnitude measured from a single observing sequence; error bars are associated with each point based on the lowest rms level detected for field stars at the corresponding brightness (see Fig. 2). The effects of interstellar reddening are traced as a vector in the bottom left quarter of each (r, u − r) diagram.