Do dark gray aluminum roller shutters get too hot?

(Mythbuster mode: ON)

Regarding all the speculations about thermal expansion, here is a pinch of facts, namely the calculation of length change due to temperature changes.

I choose extreme values:
Length of the aluminum slat of the roller shutter or venetian blind: 2 m
Temperature range: 80 °C (from -20 °C in winter to +60 °C in summer on a heated dark surface)
Thermal expansion coefficient of aluminum: 23*10E-6 m/°C

This results in a length change of 3.7 mm over the specified temperature range.

Assuming that the slats have their normal length at 20 °C and contract in the cold as well as expand in the heat,
the length change on heating (+20 °C to +60 °C) is still 1.8 mm and on cooling (+20 °C to -20 °C) also 1.8 mm.

All values are uncritical. Whether venetian blind, shutter, or roller shutter, the slats have enough play to compensate for this thermal expansion. These things are actually quite loose. Just give them a shake.

(Mythbuster mode: OFF)

Yes, that's exactly what I mean too...what exactly is the argument...because it is not the expansion...

The only thing that still happens: the hotter it is, the more heat also the inside of the roller shutters absorbs, so more heat in the house? Maybe it's about heat protection in summer?

No, that's nonsense too, then the roller shutters would be totally pointless.... they are installed because of heat protection.... there is an air gap between them and the air can also escape through the gaps, so the heat stays outside no matter what color the roller shutters are.

No, that's not nonsense. Depending on the color, different amounts of sunlight are reflected, i.e., dark shutters become significantly warmer than light/"silver" ones. The warmer the shutters, the warmer definitely is the air in the air gap – some of this heat is definitely transferred into the house (but much less than without shutters). In summer, open a window behind the closed shutters, and you will immediately notice that the air behind them is much warmer than the outside air.
Additionally, there is a second effect, thermal radiation. Hot shutters emit much more heat – also toward the window! The radiation power "goes" with the 4th power of the temperature, i.e., double the temperature leads to 16 times the radiation power! You surely know that you can feel hot radiators (70°C+) from some distance. Aluminum has a high thermal conductivity compared to plastic, so the inside is just as warm as the outside, meaning dark shutters radiate strongly toward the window.

Yes, I am also aware that the air in the air gap is hotter, but you must not forget the chimney effect, provided the shutters are not completely closed... then the air circulates and the windows or the house hardly get any of the heat... and that is how you also use the shutters. As soon as the sunlight is strong enough, you lower the shutter, but not completely so you don’t have to sit in the dark... the air circulates and the heat stays outside... completely independent of the color of the shutters. Then, for instance, the first glass pane gets a bit warmer and the frame... but everything else stays at the original temperature...