dca603d2_MacInfo___Efficiency__What_to_do
[Task] Seeing highlighted text or objects [Example] clicking and dragging to highlight [What to do] 
Make sure you have a highlight colour set that you can comfortably see. Compare these: Use System Preferences Appearance to choose a highlight colour that allows you to see clearly the beginning and end of selections for the work that you usually do.
MacInfo - Efficiency
What to do