Bagan will be without their two foreigners Sony Norde and Eduardo Ferreira who were rested because of injuries.
Coach Sanjoy Sen said he is cautious about the away game as he doesn't have too much information about the opposition.
"I don't have much knowledge about the opposition. I tried to have some idea about them by watching few of their clips on YouTube. But we have a very strong team and we are ready," Sen said on Monday.
Norde has been instrumental in Bagan's success so far and Sen was asked whether his absence in the international fixture would be a factor.
"For me all players have equal value in my side. Sony's presence definitely helps our side to be strong. But we will play cautiously as we still have the home leg remaining in this clash.
"Sony played the whole game against DSK Shivajians (in I-League). Could he alone help us to win the game? He couldn't. I believe in team game and all players are equal to me."
Mohun Bagan are presently in the second spot in I-League with 132 points from five matches.
Their opposition Colombo FC are the reigning Sri Lanka Premier League champions and have won their Football Association (FA) Cup Championship defeating Blue Star SC 1-0 in the final.