Mars’ atmosphere has the same transparency window to visible light as Earth’s. The major difference between there and here is the amount of dust suspended in the air, which is highly variable and dependent on latitude and season. On average, it actually blocks more visible light than the dust and water in Earth’s atmosphere, but the effect is also independent of wavelength, at least in the visible spectrum.

So the sky might actually be a little dimmer than you’d see in dry, dark conditions on Earth.