>>459303
That type of color saturation, contrast, opacity and general tone is characteristic of gouache paints and illustrations made with them....at the time when hand illustrations were still the norm (photo printing was expensive) and printed media likecmagazones and posters became cheap to mass produce, gouache was to go-to medium because of its speed and adaptability to a wide range of techniques...it can go on thick/opaque like oils or acrylics or be thinned to act like watercolor.
Lots of image editors have gouache filters, but learning how and why it was used is best if you want to get that effect.