Card stock that Ohuhu uses for their colour swatches?

This feels like a very random question, but does anyone know the card stock that Ohuhu uses for their colour swatches? I love how the colour sits on it (particularly the Maui markers but also the alcohol markers).

I tried searching but the closest I came was Bristol (Canson smooth Bristol was unsurprisingly too smooth, and the Strathmore vellum surface Bristol didn’t absorb the same way). It’s also much thinner (and I imagine slightly cheaper than either of those).