Both are true!
In the first case, yes steroid creams will change the colour of skin - they very slowly reduce the pigmentation, lightening the colour of the skin. The anti-inflammatory effect of the steroid reduces the activity of all skin cells, including the pigment cells - the "melanocytes".
In the second case, cellular activity in skin is stimulated by habitual scratching, and this affects all cells, including the pigment cells - the "melanocytes". So habitual scratching causes the skin to thicken up - lichenification - and colour up - hyperpigmentation. These features are characteristic of chronic atopic eczema.
In both of these cases the "problems" can be fixed by following The Combined Approach (TCA). It establishes only intermittent use of topical steroids, and with habit reversal, eliminates habitual scratching.
But it will take several months, after following The Combined Approach for just a few weeks, for these pigmentation changes to disappear - as the melanocyte activity returns to normal. The good news is that returning to normal requires no further treatment: mother nature comes to the rescue!
Before TCA After TCA
Darker, thickened skin Somewhat darker skin, normal thickness
Photographs by Iman