Trailing change his color when expanded - flutter

Question

I have this situation, I created an ExpansionTile using the code below, it is working fine, but when expanded, the trailing changes color, black to white, it was happening with the title and subtitle, but I defined the style manually to solve it, but how can I do this to trailing?
ExpansionTile(
leading: Icon(
Icons.library_music,
size: 40.0,
color: SECONDARYCOLOR,
),
title: Text(
'Pop Rock',
style: TextStyle(
fontSize: 12,
color: Colors.black,
),
),
subtitle: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
Text(
'Músicas: 30',
style: TextStyle(
fontSize: 12,
color: Colors.black,
),
),
Text(
'Duração: 2:20',
style: TextStyle(
fontSize: 12,
color: Colors.black,
),
),
],
),
children: <Widget>[
Column(
children: <Widget>[
Text('_buildExpandableContent(policies[i])'),
],
),
],
),```

Answer 1

You can easily set colours for title, subtitle, and icons (leading and trailing), both for when they are collapsed or expanded, with the following properties of the ExpandedTile:
textColor: color of title and subtitle when expanded
collapsedTextColor: color of title and subtitle when collapsed
iconColor: color of leading and trailing icons when expanded
collapsedIconColor: color of leading and trailing icons when collapsed

Answer 2

Your question look like this one: Custom style or theme for Expansion Tile Header, Flutter
I've tested a bit of code in DartPad and you can define the color for both your leading and trailing icons using something like that:
Theme(
data: Theme.of(context).copyWith(unselectedWidgetColor: SECONDARYCOLOR),
child: ExpansionTile(
leading: Icon(Icons.library_music, size: 40.0),
title: Text(
'Pop Rock',
style: TextStyle(
fontSize: 12,
color: Colors.black,
),
),
subtitle: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
Text(
'Músicas: 30',
style: TextStyle(
fontSize: 12,
color: Colors.black,
),
),
Text(
'Duração: 2:20',
style: TextStyle(
fontSize: 12,
color: Colors.black,
),
),
],
),
children: <Widget>[
Column(
children: <Widget>[
Text('_buildExpandableContent(policies[i])'),
],
),
],
),
)

Answer 3

In my case to support both states - collapsed and expanded - for icon color, had to use a combination of the following:
In ExpansionTile set property: iconColor
Widget expansionTile = ExpansionTile(
iconColor: Colors.white,
title: Text('Visible'),
children: [
Text('Expanded element')
]
);
Then wrap that in a Theme, and set: unselectedWidgetColor
expansionTile = Theme(
data: Theme.of(_ctxt).copyWith(
unselectedWidgetColor: Colors.white,
),
child: expansionTile);