Question

what are universal indicator.. ?

Answer 1

universal indicators

a mixture of dyes that changes colour gradually over a range of pH and is used (especially as indicator paper) in testing for acids and alkalis.

Answer 2

A Universal Indicator is defined as a mixture having many indicators of wide pH range. To obtain universal indicators, many indicators are mixed( though it behave as a single indicator) so that they can have a change in color over a wider pH range.
Kolthoff is a universal indicator