Red
The radical for red and the kanji for red are the same thing!
What a lucky ducky - as long as you know your radicals, you'll know this kanji's meaning as well!
せき
あか
None
This kanji means red, AKA, also known as, あか.
Think of あか as being some sort of alias for "red." That's why its pronounced あか in Japanese, AKA "red."