  HD 95086 is an intermediate-mass debris-disk-bearing star. VLT/NaCo $3.8 \mu
m$ observations revealed it hosts a $5\pm2 \mathrm{M}_{Jup}$ companion (HD
95086 b) at $\simeq 56$ AU. Follow-up observations at 1.66 and 2.18 $\mu m$
yielded a null detection, suggesting extremely red colors for the planet and
the need for deeper direct-imaging data. In this Letter, we report H- ($1.7 \mu
m$) and $\mathrm{K}_1$- ($2.05 \mu m$) band detections of HD 95086 b from
Gemini Planet Imager (GPI) commissioning observations taken by the GPI team.
The planet position in both spectral channels is consistent with the NaCo
measurements and we confirm it to be comoving. Our photometry yields colors of
H-L'= $3.6\pm 1.0$ mag and K$_1$-L'=$2.4\pm 0.7$ mag, consistent with
previously reported 5-$\sigma$ upper limits in H and Ks. The photometry of HD
95086 b best matches that of 2M 1207 b and HR 8799 cde. Comparing its spectral
energy distribution with the BT-SETTL and LESIA planet atmospheric models
yields T$_{\mathrm{eff}}\sim$600-1500 K and log g$\sim$2.1-4.5. Hot-start
evolutionary models yield M=$5\pm2$ M$_{Jup}$. Warm-start models reproduce the
combined absolute fluxes of the object for M=4-14 M$_{Jup}$ for a wide range of
plausible initial conditions (S$_{init}$=8-13 k$_{B}$/baryon). The
color-magnitude diagram location of HD 95086 b and its estimated
T$_{\mathrm{eff}}$ and log g suggest that the planet is a peculiar L-T
transition object with an enhanced amount of photospheric dust.
