Given:
\[
\sec^2 \theta = \frac{4}{3}
\]
Using the identity:
\[
\sec^2 \theta = 1 + \tan^2 \theta
\]
Substituting:
\[
1 + \tan^2 \theta = \frac{4}{3}
\]
\[
\tan^2 \theta = \frac{4}{3} - 1 = \frac{1}{3}
\]
\[
\tan \theta = \pm \frac{1}{\sqrt{3}}
\]
The general solution for \( \tan \theta = \pm \frac{1}{\sqrt{3}} \) is:
\[
\theta = n\pi \pm \frac{\pi}{6}, \quad n \in \mathbb{Z}
\]
Thus, the correct answer is \( n\pi \pm \frac{\pi}{6} \).