  In the present paper, we investigate the quasinormal modes of an
Einstein-Maxwell power-Yang-Mills black hole in four dimensions, considering a
specific value of the power parameter $p = 1/2$. This particular case
represents a black hole with both Abelian and Non-Abelian charges and is
asymptotically non-flat. We begin by deriving the effective potential for a
neutral massless particle using the aforementioned black hole solution.
Subsequently, employing the sixth-order WKB approximation method, we calculate
the (scalar) quasinormal modes. Our numerical analysis indicates that these
modes are stable within the considered parameter range. This result is also
confirmed using the eikonal approximation. Furthermore, we calculate the shadow
radius for this class of black hole and derive constraints on the electric and
Yang-Mills charges ($Q,Q_{\rm YM}$) by using imaging observational data for Sgr
A${^\star}$, provided by the Event Horizon Telescope Collaboration. We observe
that as the electric charge $Q$ increases, the allowed range shifts towards
negative values of $Q_{\rm YM}$. For instance, for the maximum value $Q\approx
1.1$ obtained, the allowed range becomes $-0.171 \lesssim Q_{\rm YM} \lesssim
-0.087$ consistent with KECK and VLTI data, while still retaining a
non-vanishing horizon.
