One of the issues I have noticed when using several of the K2 SmartForm themes is that when you have a read-only or disabled view/control, which is a very common scenario, the label and text box values that someone may have entered in the form appear very hard to see or read.
The default CSS file of SmartForms applies a opacity :0.5 and changes the color of the labels and textboxes to a light gray, making it hard to read what a person entered in the field.

If you are familiar with CSS branding and styling, this shouldn't be a problem for you to modify or when creating a new theme.
Here are the steps to modify the default theme without having to create your SmartForm theme:
- Modify the core.css file located at C:\Program Files (x86)\K2 blackpearl\K2 SmartForms Runtime\Styles\Themes\
- Search for classes with ".disabled" appended to them for span, textboxes and labels.
- Either comment out the opacity: 0.5; lines or change to 1.0
- Find this line: .theme-entry label.input-control.disabled .input-control-text { color:#999; }
- and change the color to black (#000 or #333)