Use the below code for black:
<color name="black">#000000</color>
Now if I want to use opacity then you can use the below code:
<color name="black">#99000000</color> <!-- 99 is for alpha and others pairs zero's are for R G B -->
And below for opacity code: and all opacity level here
Hex Opacity Values
100% — FF
95% — F2
90% — E6
85% — D9
80% — CC
75% — BF
70% — B3
65% — A6
60% — 99
55% — 8C
50% — 80
45% — 73
40% — 66
35% — 59
30% — 4D
25% — 40
20% — 33
15% — 26
10% — 1A
5% — 0D
0% — 00
If you always to forget what code for transparency then you must have to see below link and no worry about to remember anything regarding transparent code :-
https://github.com/duggu-hcd/TransparentColorCode
textviewHeader.setTextColor(Color.parseColor(ColorTransparentUtils.transparentColor(R.color.border_color,10)));