Hi @Tushar_07,
You cannot colorize cells in data tables (output data ports). The Color Manager node add a color tag to the rows in data tables. This color tag can be used to colorize data views (i.e. JavaScript views).
If you like to colorize cells in the output XLS file, you can use Continental nodes. Here is an example workflow at KNIME Hub:
P.S. BIRT can also do that for you: