Colouring a button in Qt - qt

Question

I'm trying to design a simple button (QPushButton or QToolButton, either can work) that would essentially be a rectangle of the colour it represents. Clicking it opens a QColorDialog, and selecting a colour in it repaints the button.
So, basically, something that will look like one of these:
I made a few attempts, none of which brought me the functionality I wanted.
Slot:
void MainWindow::OnButtonColorClick()
{
QColor initialColor = ui->buttonColor->palette().color(QPalette::Background);
QColor colorSelected = QColorDialog::getColor(initialColor, this);
if(colorSelected.isValid())
{
ui->buttonColor->setPalette(QPalette(colorSelected));
ui->buttonColor->setAutoFillBackground(true);
}
}
Attempt #1:
Set the Palette in the constructor:
ui->buttonCoulor->setPalette(QPalette(Qt::black));
Result: ordinary button before click, thin coloured contour after selection.
Attempt #2:
Add stylesheet:
background-color: rgb(0, 0, 0);
Result: black rectangle before click, black rectangle after selection.
I feel like I'm circling the drain. Essentially, how do I achieve:
?

Answer 1

Here is one way to accomplish the desired effect:
// Slot for the button
void MainWindow::on_button()
{
QColor color = QColorDialog::getColor();
QString s("background: #"
+ QString(color.red() < 16? "0" : "") + QString::number(color.red(),16)
+ QString(color.green() < 16? "0" : "") + QString::number(color.green(),16)
+ QString(color.blue() < 16? "0" : "") + QString::number(color.blue(),16) + ";");
button->setStyleSheet(s);
button->update();
}
Hope that helps.

Answer 2

use setStyleSheet with this style sheet:
border: 1px solid black;
background-color: #XXXXXX;
where XXXXXX is the value returned by QString::number(myColor.rgb(), 16).toUpper();
No need to set any other properties on the button. Leave them all as default and this will work.

Answer 3

This seems to be working just fine for me:
if(colorSelected.isValid())
{
ui->buttonColor->setPalette(QPalette(colorSelected));
}

Answer 4

As a follow-up to phyatt's answer, there's a shortcut to generate the XML-formatted color string:
QString s("background: " + color.name + ";");
button->setStyleSheet(s);