Purple is replacing red as the color of choice for teachers. Why, you may ask? It seems that educators worry that emphatic red corrections on a homework assignment or test can be stressful, demeaning--even "frightening" for a young person. The principal of Thaddeus Stevens Elementary in Pittsburgh advises teachers to use only "pleasant-feeling tones."Major pen manufacturers appear to agree. Robert Silberman, vice president of marketing at Pilot Pen, says teachers "are trying to be positive and reinforcing rather than harsh." Michael Finn, a spokesperson for Paper Mate, approves: "This is a kinder, more gentle education system." Which color is...