In a right triangle, the sum of the acute angles \( \theta \) and \( \phi \) is \( 90^\circ \). Therefore, we have:
\[ \theta + \phi = 90^\circ \]
This means that:
\[ \theta = 90^\circ - \phi \]
Using the co-function identity for cosine and sine, we know that:
\[ \cos(\theta) = \sin(90^\circ - \theta) = \sin(\phi) \]
Given that \( \sin(\phi) = 0.25 \), we can substitute:
\[ \cos(\theta) = \sin(\phi) = 0.25 \]
Thus, the value of \( \cos \theta \) is:
\[ \boxed{0.25} \]