We have monitored the BL Lac object Mrk 501 in optical V , R and I bands from 2010 to 2015 .
For Mrk 501 , the presence of strong host galaxy component can affect the results of photometry .
After subtracting the host galaxy contributions , the source shows intraday and long-term variabilities for optical flux and color indices .
The average variability amplitudes of V , R and I bands are 22.05 \%, 22.25 \%, 23.82 \% respectively , and the value of duty cycle 14.87 per cent .
A minimal variability timescale of 106 minutes is detected .
No significant time lag between V and I bands is found on one night .
The bluer-when-brighter ( BWB ) trend is dominant for Mrk 501 on intermediate , short and intraday timescales which supports the shock-in-jet model .
For the long timescale , Mrk 501 in different state can have different BWB trend .
The corresponding results of non-correcting host galaxy contributions are also presented .