In the pre-digital era, industrial designers had to keep a decent stock of colored Canson paper on hand for renderings. I still remember buying these as a design student; with little funds, I’d get no more than five at a time in random colors, at least one of them dark grey.
In this video, industrial designer Michael DiTullo discusses both the history and merits of sketching on toned paper, then demonstrates with a sneaker sketch:
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Source: core77