https://userapps.support.sap.com/sap/support/knowledge/en/3417433
3417433 - Fiori Horizon family themes not available | SAP Knowledge Base Article
Some Horizon themes are unavailable in Fiori. Example: Evening Horizon and High Contrast Black are not available, but Morning Horizon and High Contrast White...
horizon familynot availablesap knowledgefiorithemes