We report on simultaneous g ^ { \prime } , R _ { c } and I _ { c } photometry of SU Ursae Majoris during 2011 December - 2012 February using OAO/MITSuME .
Our photometry revealed that quiescence is divided into three types based on the magnitude and color .
Quiescent light curves showed complicated profiles with various amplitudes and time scales .
Although no superoutbursts were observed during our run , five normal outbursts occurred with intervals of 11 - 21 d. The shapes of the normal outbursts were characteristic of the outside-in type .
During the rising phase of a normal outburst , the light curve showed periodic modulations with a period of { \sim } 0.048111 ( 354 ) d , but the origin of this peirod was unclear .
We examined daily averaged color-color diagram and found that two cycles exist .
This implies that the thermal limit cycle in SU UMa is complicated .
We newly discovered that g ^ { \prime } - R _ { c } becomes red about 3 days prior to an outburst .
Although the working mechanism on this reddening is unclear , we propose two possibilities : one is that the inner portion of the accretion disk is filled by matter and obscures the central white dwarf , and the other is that the stagnation effect works in the outer region of the accretion disk .