Is possible to change the faded text for weekends? You can hardly see it!

Yes, it is. BreezingForms calls the Joomla calendar function into the form. You should find their CSS file here:

 JOOMLA\media\system\css\calendar-jos.css

 And here is the CSS you are looking for (around line 42): 

.calendar thead .name {
	border-bottom: 1px solid #cccccc;
	padding: 2px;
	text-align: center;
	color: #000;
}

.calendar thead .weekend { 
	color: #999;
}  

It's the 'weekend' part of that you need to change.