1:
Admin CP > Languages & Phrases > Search in Phrases
Search for: sticky_thread_prefix
Search in...: Phrase Variable Name Only
Once found, click 'edit'. In the space provided, enter:
<span class="stickyprefix">Sticky:</span>
2:
Admin CP > Style Manager > Style you want to change
All Style Options > Go
In Additional CSS Definitions add:
.stickyprefix { color:#FF4400; font-weight:bold; }
Done
The above will change the style of 'Sticky:" to Bold Red text. If a color other than red is desired, change FF4400 to your liking. Additionally, if you do not want the text bolded, remove: font-weight:bold;