Unique Children

Mr. and Mrs. Tan have four children--three boys and a girl--
who each like one of the colors--blue, green, red, yellow--
and one of the letters--P, Q, R, S.

1. The oldest child likes the letter Q.
2. The youngest child likes green.
3. Alfred likes the letter S.
4. Brenda has an older brother who likes R.
5. The one who likes blue isn't the oldest.
6. The one who likes red likes the letter P.
7. Charles likes yellow.

Based on the above facts, Darius is the $\text{\_\_\_\_\_\_\_\_\_\_}.$