Get the Time of Last update of a column
None of the system tables (that is, nothing in the INFORMATION_SCHEMA database) exist that has that kind of information recorded anywhere. In other words, there is no native mechanism to put any timestamps on column changes. Any time that


one or more columns change in any row
a new row is added
an old is deleted
an ALTER TABLE of any kind


the UPDATE_TIME column in INFORMATION_SCHEMA.TABLES is updated. 

SUGGESTION

This may be a bitter pill to swallow, but you must do the following:


Create a custom table that records

primary key
column name
the old value of that column
the new value of that column
timestamp of the change

Create BEFORE UPDATE trigger to compare old and new columns and record it if they do not match


EPILOGUE

This may not be so bad if you are customizing for a few tables and a few columns.