Sodium hydroxide (NaOH) is a strong base. Bromothymol blue is a pH indicator that changes color depending on the acidity or alkalinity of the solution. Here's how it works:

* In acidic solutions: Bromothymol blue is yellow.

* In neutral solutions: Bromothymol blue is green.

* In basic solutions: Bromothymol blue is blue.

Since sodium hydroxide is a strong base, it will make the solution highly alkaline. Therefore, the color of sodium hydroxide in bromothymol blue will be blue.