I use KDE 4.10 with air theme. I cannot read the window names in the taskbar:



is there a setting for font color or opacity of the taskbar?

Opacity is determined by the Plasma theme in use, and by the activation state of the Blur desktop effect. There is no way to set opacity manually short of either:

a. changing the current Plasma theme
b. mixing a differently-opaque panel from another theme using the control module in System Settings (Workspace appearance)