Why does the colour in my xml file in android studio show purple and not black?

Question

I have added the background colour of a button to be black and yet for some reason the background colour is a purple in the design view and when I run the app on my device. On the side of my code it clearly shows that the colour is black by showing me a black square, this is only happening with this colour, I have also tried using @color/black, and #FF000000 yet nothing works. I have checked my color.xml file and it shows black as #FF000000. What is going on? #000 is suppose to black I even checked.

<Button
                    android:id="@+id/bac"
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    android:layout_weight="1"
                    android:background="#000"
                    android:text="AC"
                    android:textColor="#33ccff"
                    android:textSize="23sp">

                </Button>