As discussed on IRC: 

The channel mode button states are in some themes, e.g. the default breeze, hard to distinguish. Thus one can't tell which channel modes are enabled or disabled.

Reproducible: Always

Steps to Reproduce:
1. Use the default theme in KF5 konvi (breeze)
2. Enable channel mode buttons
3. Look at them

Actual Results:  
Hard to tell which ones are active and which ones aren't

Expected Results:  
easily distinguishable

as discussed on IRC:  probably something like the toggle buttons in toolbars would be perfect, as they 

1) are meant to be distinguishable and thus should work in most, if not all Qt themes
2) are consistent with other applications