How to animate TextSpans within Flutter TextFormField - flutter

Question

I am currently working on a project that requires minor animations to text as it appears in a TextFormField.
I hav extended the TextEditingControler and overriden the buildTextSpan function to enable different TextSyles based on the types of words that were being typed in. For example if a word is ['the','a','me'].
For example I would add a TextSpan with a particular style for each matching word and for all other words I would just add the word in a TextSpan with normal style.
This is working fine, however, what I want to do is to animate the matched words for a period as they are entered, for example they would turn from blue to green.
Extended TextEditingController Class
class RichTextEditingController extends TextEditingController {
TextStyle matchedStyle = TextStyle(
color: Colors.green,
fontSize: 20,
fontWeight: FontWeight.w700,
);
#override
TextSpan buildTextSpan({TextStyle style, bool withComposing}) {
List<String> wordsToMatchList = ['the','a','me'];
List<String> splitText = text.split(' ');
List<TextSpan> textSpanList = [];
splitText.forEach((word) {
if (wordsToMatchList.contains(word)) {
textSpanList.add(TextSpan(style: boldStyle, text: '$word'));
} else {
textSpanList.add(TextSpan(style: style, text: '$word'));
}
});
return TextSpan(children: textSpanList);
}
}
I have tried various techniques like future.Delayed and others, but can't seem to find any approach that works and need some help.
Question: Is there a way to add a minor animation to TextSpans or other widgets that would show when new text is typed into a text field that matches a certain pattern?