#include <QTextCursor>
#include <QTextCharFormat>
 
void MainWindow::on_pushButton_clicked()
{
    QTextCharFormat fmt = ui->textEdit->currentCharFormat();
    fmt.setForeground(QColor ("red"));
    ui->textEdit->setCurrentCharFormat(fmt);
    ui->textEdit->insertPlainText("Abc ");
 
    QTextCursor c = ui->textEdit->textCursor();
    QTextCharFormat f = c.charFormat();
    f.setForeground(QColor ("blue"));
    c.setCharFormat(f);
    c.insertText("Def ");
}