If memory serves me right, the color red was used long before Marx and Engels, perhaps because it has been perceived as a graphically vibrant and dynamic color, or because of its association with blood and fire, as a revolutionary color, a call to action, a call to arms. On the other hand, the color white has signified purity, passivity, subservience, etc.
During the birth Soviet Era, El Lissitzky painted a poster which captured the spirit of the moment, BEAT THE WHITES WITH THE RED WEDGE. Following is a description of the poster from
http://www.foulfiend.com/thesis/text15.htm"Lissitzky's ... most famous abstract poster is perhaps his 1920 Beat the Whites with the Red Wedge. The completely conceptual format of the work does not interfere with the effectiveness of the message, which relies on the evocative nature of the forms: the active character of the sharp triangular wedge, which disrupts the passive white circle. The dynamism of the composition relies on the relationship between the positive and negative space created by clear geometric forms and red and black colors on the white background. The mirror images of the black and white equally divided background, are made asymetric by the low position of the large white circular form. The latter looks as if is not only being shattered by the focused triangle of red, but as if it is also falling toward the bottom and out of the image. As this is happening, small pieces of the white and the red are flying off into the space around it. The text flows diagonally from the upper left corner into the lower right corner and thereby covers the whole area of the poster. Nothing is missed by the eye, since the viewer sees the large negative space of the white circle first, after which the eye is drawn to the empty upper left corner, where the heavy black text begins with the short bold revolutionary slogan in the poetic style of Mayakovsky".
