ותתן לנו את יום הכפורים הזה
Why is the word (כפורים) plural and not singular like the other descriptions of the day (יום סליחה, יום מחילה)?
Perhaps, one can explain by understanding that Teshuvah can function in steps, and thus the forgiveness can be in multiple levels (thus plural word כפורים).
This concept of multiple levels is symbolized by the description of white; sometimes the forgiveness is described by white as snow (solid color, a complete forgiveness) and other times by white as wool (a less bold color of white, an incomplete forgiveness).
Similarly, the “size” of the sin can be expressed by different levels of the color red, crimson (blood) red or a duller shade of red. The amount of heating of the blood (passion of feeling) involved in the sin is reflected in the boldness of the color of red.
In Parshas Chukas, Rashi (19,22) explains the reason for the name Parah Adumah is due to this offering comes for atonement of the sin (of the Calf), and sin is called אדום red. However, it does not explain why the color is used to indicate this idea.
Now, we can understand red since this concept of that color reflects levels of involvement and effort in doing wrong as reflected of the redness in the face. And the sin of the Calf was due to great effort. Thus, this sacrifice utilizes the deep color of red in order to bring the level of forgiveness that is needed to overcome the great deal of effort involved in this sin.
