If several accounts are displayed in the Samsung calendar, the calendar offers us a function to differentiate between the individual accounts. In the settings we can assign a different colour to each account or calendar.

If, for example, we want the holidays to be in yellow instead of green, this can be easily set.

Android 10 (One UI 2.0)
Step 1:  Open the  Calendar -App
Step 2:  Open the  menu
Step 3:  Open the  Settings
Step 4:  Tap on  Manage calendar colours
Step 5:  Tap on desired  Account
Step 6:  Choose desired  Colour
  1. Open the Calendar-App
  2. Open the menu
  3. Open the Settings
  4. Tap on Manage calendar colours
  5. Tap on desired Account
  6. Choose desired Colour

Samsung Instructions