Changing EditText bottom line color with appcompat v7

Finally, I have found a solution. It simply consists of overriding the value for colorControlActivated, colorControlHighlight and colorControlNormal in your app theme definition and not your edittext style. Then, think to use this theme for whatever activity you desire. Below is an example:

<style name="Theme.App.Base" parent="Theme.AppCompat.Light.DarkActionBar">
    <item name="colorControlNormal">#c5c5c5</item>
    <item name="colorControlActivated">@color/accent</item>
    <item name="colorControlHighlight">@color/accent</item>
</style>

I felt like this needed an answer in case somebody wanted to change just a single edittext. I do it like this:

editText.getBackground().mutate().setColorFilter(ContextCompat.getColor(context, R.color.your_color), PorterDuff.Mode.SRC_ATOP);

While Laurents solution is correct, it comes with some drawbacks as described in the comments since not only the bottom line of the EditText gets tinted but the Back Button of the Toolbar, CheckBoxes etc. as well.

Luckily v22.1 of appcompat-v7 introduced some new possibilities. Now it's possible to assign a specific theme only to one view. Straight from the Changelog:

Deprecated use of app:theme for styling Toolbar. You can now use android:theme for toolbars on all API level 7 and higher devices and android:theme support for all widgets on API level 11 and higher devices.

So instead of setting the desired color in a global theme, we create a new one and assign it only to the EditText.

Example:

<style name="MyEditTextTheme">
    <!-- Used for the bottom line when not selected / focused -->
    <item name="colorControlNormal">#9e9e9e</item>
    <!-- colorControlActivated & colorControlHighlight use the colorAccent color by default -->
</style>

<EditText
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:theme="@style/MyEditTextTheme"/>

This can be changed in XML by using:

For Reference API >= 21 compatibility use:

android:backgroundTint="@color/blue"

For backward API < 21 compatibility use:

app:backgroundTint="@color/blue"

Here is the solution for API < 21 and above

Drawable drawable = yourEditText.getBackground(); // get current EditText drawable 
drawable.setColorFilter(Color.GREEN, PorterDuff.Mode.SRC_ATOP); // change the drawable color

if(Build.VERSION.SDK_INT > 16) {
    yourEditText.setBackground(drawable); // set the new drawable to EditText
}else{
    yourEditText.setBackgroundDrawable(drawable); // use setBackgroundDrawable because setBackground required API 16
}

https://i.stack.imgur.com/wu1yD.png

Hope it help

The accepted answer is a bit more per style basis thing, but the most efficient thing to do is to add the colorAccent attribute in your AppTheme style like this:

<style name="AppTheme.Base" parent="Theme.AppCompat.Light.NoActionBar">
        <item name="colorAccent">@color/colorAccent</item>
        <item name="android:editTextStyle">@style/EditTextStyle</item>
</style>

<style name="EditTextStyle" parent="Widget.AppCompat.EditText"/>

The colorAccent attribute is used for widget tinting throughout the app and thus should be used for consistency

If you are using appcompat-v7:22.1.0+ you can use the DrawableCompat to tint your widgets

    public static void tintWidget(View view, int color) {
        Drawable wrappedDrawable = DrawableCompat.wrap(view.getBackground());
        DrawableCompat.setTint(wrappedDrawable.mutate(), getResources().getColor(color));
        view.setBackgroundDrawable(wrappedDrawable);
    }

<!-- Base application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
    <!-- Customize your theme here. -->
    <item name="colorPrimary">@color/colorPrimary</item>
    <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
    <item name="colorAccent">@color/colorAccent</item>

    <item name="colorControlNormal">@color/colorAccent</item>
    <item name="colorControlActivated">@color/colorAccent</item>
    <item name="colorControlHighlight">@color/colorAccent</item>

</style>

Use:

<EditText
    app:backgroundTint="@color/blue"/>

This will support pre-Lollipop devices not only +21