Chapter 17, Problem 39QP

The ionization constant $K_{\text{a}}$ of an indicator $\text{HIn}$ is $\text{1}\text{.0 }\times {\text{ 10}}^{\text{-6}}\text{.}$ The color of the nonionized form is red and that of the ionized form is yellow. What is the color of this indicator in a solution whose pH is 4.00?