<style name="TextAppearance.App.TextInputLayout" parent="@android:style/TextAppearance">
    <item name="android:textColor">@color/red</item>
    <item name="android:textSize">14sp</item>
</style>

<android.support.design.widget.TextInputLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:textColorHint="@color/gray"  //support 23.0.0
    app:hintTextAppearance="@style/TextAppearence.App.TextInputLayout" >

    <android.support.v7.widget.AppCompatEditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="@string/hint" />
</android.support.design.widget.TextInputLayout>

在最新版本的支持库(23.0.0+)中，TextInputLayout采用以下XML属性来编辑浮动标签颜色:

更改提示颜色和编辑文本下划线颜色:colorControlActivated

更改字符计数器颜色:textColorSecondary

更改错误信息的颜色:colorControlNormal

要更改密码可见性按钮颜色:colorForeground

更多关于TextInputLayout的信息请阅读http://www.zoftino.com/android-textinputlayout-tutorial

<style name="MyAppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
    <item name="colorPrimary">@color/colorPrimary</item>
    <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
    <item name="colorControlActivated">#e91e63</item>
    <item name="android:colorForeground">#33691e</item>
    <item name="colorControlNormal">#f57f17</item>
    <item name="android:textColorSecondary">#673ab7</item>
</style>

有太多复杂的解决方案。下面是一个改变浮动标签颜色的程序。

<com.google.android.material.textfield.TextInputLayout
   app:hintTextColor="@color/white"/>

除了更改其他属性:

更改框描边颜色:

<com.google.android.material.textfield.TextInputLayout
    app:boxStrokeColor="@color/green"

更改方框描边宽度:

<com.google.android.material.textfield.TextInputLayout 
     app:boxStrokeWidth="1.5dp"

更改编辑TextInputEditText提示颜色:

<com.google.android.material.textfield.TextInputEditText
     android:textColorHint="@color/white"

更改TextInputEditText的颜色:

<com.google.android.material.textfield.TextInputEditText           
            android:textColor="@color/white" />

从文档中可以看到:

提示应该设置在TextInputLayout上，而不是EditText上。如果在XML中的子EditText上指定了提示，TextInputLayout可能仍然正确工作;TextInputLayout将使用EditText的提示作为浮动标签。但是，将来修改提示的调用将不会更新TextInputLayout的提示。为了避免意外的行为，在TextInputLayout上调用setHint(CharSequence)和getHint()，而不是在EditText上。

所以我设置android:hint和app:hintTextColor在TextInputLayout，而不是在TextInputEditText和它工作。

你可以在程序上使用:

/* Here you get int representation of an HTML color resources */
int yourColorWhenEnabled = ContextCompat.getColor(getContext(), R.color.your_color_enabled);
int yourColorWhenDisabled = ContextCompat.getColor(getContext(), R.color.your_color_disabled);

/* Here you get matrix of states, I suppose it is a matrix because using a matrix you can set the same color (you have an array of colors) for different states in the same array */
int[][] states = new int[][]{new int[]{android.R.attr.state_enabled}, new int[]{-android.R.attr.state_enabled}};

/* You pass a ColorStateList instance to "setDefaultHintTextColor" method, remember that you have a matrix for the states of the view and an array for the colors. So the color in position "colors[0x0]" will be used for every states inside the array in the same position inside the matrix "states", so in the array "states[0x0]". So you have "colors[pos] -> states[pos]", or "colors[pos] -> color used for every states inside the array of view states -> states[pos] */
myTextInputLayout.setDefaultHintTextColor(new ColorStateList(states, new int[]{yourColorWhenEnabled, yourColorWhenDisabled})

解释:

Get int color value from a color resource (a way to present rgb colors used by android). I wrote ColorEnabled, but really it should be, for this answer, ColorHintExpanded & ColorViewCollapsed. Anyway this is the color you will see when the hint of a view "TextInputLayout" is on Expanded or Collapsed state; you will set it by using next array on function "setDefaultHintTextColor" of the view. Reference: Reference for TextInputLayout - search in this page the method "setDefaultHintTextColor" for more info

查看上面的文档，你可以看到函数通过使用ColorStateList来设置展开和折叠提示的颜色。

ColorStateList docs

To create the ColorStateList I first created a matrix with the states I want, in my case state_enabled & state_disabled (whose are, in TextInputLayout, equals to Hint Expanded and Hint Collapsed [I don't remember in which order lol, anyway I found it just doing a test]). Then I pass to the constructor of the ColorStateList the arrays with int values of color resources, these colors have a correspondences with the states matrix (every element in colors array correspond to the respective array in states matrix at same position). So the first element of the colors array will be used as color for every state in the first array of the states matrix (in our case the array has only 1 element: enabled state = hint expanded state for TextInputLayut). Last things states have positive / negative values, and you have only the positive values, so the state "disabled" in android attrs is "-android.state.enabled", the state "not focused" is "-android.state.focused" ecc.. ecc..

希望这对你有帮助。 再见，祝你编码愉快。