Study the following statements about Gram staining: [P]: Gram positive bacteria are stained deep violet and Gram negative bacteria are stained red. [Q]: Gram positive bacteria are stained red and Gram negative bacteria are stained deep violet. [R]: The sequence of addition of staining reagents is crystal violet, iodine solution, alcohol and safranin. [S]: In Gram positive bacteria the purple color developed during staining is lost during alcohol treatment. The cells later take up the safranin and stain red. Choose the correct combination of statements.