You can change the collation of a column using alter table, for example assuming your column is a VARCHAR(40)
:
alter table YourTable modify YourColumn varchar(40) collate utf8_bin;
If you don't want any collation at all change the column type to binary, varbinary or blob:
alter table YourTable modify YourColumn varbinary(40);
You can also change the default collation of a table but it only affects columns you create afterwards.