▁and ▁equally ▁in ▁the ▁physical ▁mixture ▁of ▁p ig ments ▁or ▁d yes . ▁These ▁theories ▁were ▁en hanced ▁by ▁ 1 8 th - century ▁investig ations ▁of ▁a ▁variety ▁of ▁purely ▁psych ological ▁color ▁effects , ▁in ▁particular , ▁the ▁contrast ▁between ▁" com plement ary " ▁or ▁oppos ing ▁h ues ▁produced ▁by ▁color ▁after images ▁and ▁in ▁the ▁contrast ing ▁sh adows ▁in ▁colored ▁light . ▁These ▁ideas ▁and ▁many ▁personal ▁color ▁observations ▁were ▁summar ized ▁in ▁two ▁found ing ▁documents ▁in ▁color ▁theory : ▁the ▁Theory ▁of ▁Colors ▁( 1 8 1 0 ) ▁by ▁the ▁German ▁poet ▁and ▁government ▁minister ▁Johann ▁Wolfgang ▁von ▁Go ethe , ▁and ▁The ▁Law ▁of ▁Sim ult aneous ▁Color ▁Con tr ast ▁( 1 8 3 9 ) ▁by ▁the ▁French ▁industrial ▁chem ist ▁Michel - E ug ène ▁Che vre ul . ▁ ▁In ▁late ▁ 1 9 th ▁and ▁early ▁to ▁mid - 2 0 th - century ▁commercial ▁printing , ▁use ▁of ▁the ▁traditional ▁R Y B ▁termin ology ▁pers isted ▁even ▁though ▁the ▁more ▁vers atile ▁C MY ▁( cy an , ▁mag enta , ▁yellow ) ▁tri ad ▁had ▁been ▁adopted , ▁with ▁the ▁cy an ▁sometimes ▁referred ▁to ▁as ▁" process ▁blue " ▁and ▁the ▁mag enta ▁as ▁" process ▁red ". ▁ ▁C MY ▁and ▁C MY K ▁color ▁models ▁and ▁printing ▁processes ▁▁ ▁In ▁color ▁printing , ▁the ▁usual ▁primary ▁colors ▁are ▁cy an , ▁mag enta ▁and ▁yellow ▁( C MY ). ▁Cy