* Επτά αλήθειες (Eptá alítheies): This is the most literal translation. "Επτά" (Eptá) means seven, and "αλήθειες" (alítheies) is the plural of "αλήθεια" (alítheia), meaning truth. This is suitable in most contexts.
* Επτά αληθείς (Eptá alitheís): This is a slightly less common but grammatically correct alternative. It uses the plural masculine form of "true" ("alitheís") instead of the plural of "truth." This might be used if the "truths" are presented as true statements rather than abstract concepts.
The best option is Επτά αλήθειες (Eptá alítheies) for general use.