This answer is based on the assumption that the President can pardon himself. It's not exactly clear if the President can do so as the Constitution neither allows or disallows it explicitly.
Yes, anyone pardoned for a specific crime can still be charged for other crimes that he was not pardoned for.
However, the example that you've cited – "collusion", is relatively broad and there's no one crime that covers it. So, it would make more sense to issue a broader pardon, as explained below.
The President can issue a presidential pardon for all offenses committed during a certain period.
An example is the presidential pardon issued by Gerald Ford to his predecessor Richard Nixon.
The text of Ford’s Pardon Proclamation is as follows:
Now, THEREFORE, I, GERALD R. FORD, President of the United States, pursuant to the pardon power conferred upon me by Article II, Section 2, of the Constitution, have granted and by these presents do grant a full, free, and absolute pardon unto Richard Nixon for all offenses against the United States which he, Richard Nixon, has committed or may have committed or taken part in during the period from January 20, 1969 through August 9, 1974.