fig, ax = plt.subplots(1,1,figsize=(10,10))
ax.scatter(HUGScolor, HUGSmag,s=1,c=HUGSdensity, cmap="Reds")
ax.scatter(ACScolor, ACSmag, s=1,c=ACSdensity, cmap='Blues', alpha=0.1)
ax.set_ylim(17, 22)
ax.invert_yaxis()
ACSSmoothTCK = splrep(ACSFiducial[0].mean[1], ACSFiducial[0].mean[0], s=0.001)
ax.plot(BSpline(*ACSSmoothTCK)(ACSFiducial[0].mean[1]), ACSFiducial[0].mean[1] , color='C0')
HUGSmoothTCK = splrep(HUGSFiducial[0].mean[1], HUGSFiducial[0].mean[0], s=0.001)
ax.plot(BSpline(*HUGSmoothTCK)(HUGSFiducial[0].mean[1]), HUGSFiducial[0].mean[1] , color='C1')
ax.set_xlim(0.6, 1)

ax.set_xlabel("F606W - F814W", fontsize=27)
ax.set_ylabel("F606W", fontsize=27)

Color = isoMags['WFC3_UVIS_F606W'].values - isoMags["WFC3_UVIS_F814W"].values
Mag = isoMags['WFC3_UVIS_F606W'].values
turnOffColor = min(Color)
turnOffMag = Mag[Color==turnOffColor][0]
print(turnOffMag, turnOffColor)

ax.plot(Color, Mag, color='C2', linewidth=10)