  In this paper, we show that the optically bright stars above the tip of the
first red giant branch (TRGB) in the color magnitude (CM) diagrams of nearby
dwarf elliptical (dE) galaxies, commonly interpreted as indication of the
existence of an intermediate-age population, may, in certain circumstances, be
an artifact of observational effects on a pure old population system. For this
purpose, model CM diagrams have been computed simulating the observational
effects that can be found in different regions of a Local Group dE galaxy. The
starting synthetic CM diagram represents a pure old system, with star formation
extending only from 15 to 12 Gyr ago. Based on those model diagrams, we analyze
the conclusions that a hypothetical ground-based observer might reach
concerning the presence of a population of stars above the tip of the red giant
branch (TRGB) that could be interpreted as an intermediate-age population, by
using two age indicators extensively employed in the literature: i) the
bolometric magnitude at the tip of the asymptotic giant branch (AGB) phase, and
ii) the ratio of AGB to red giant branch (RGB) stars present in the CM diagram.
Our analysis shows that, if observational effects are overlooked, application
of both methods would result in finding a fictitious intermediate-age
population in the inner regions of the galaxy, where crowding is more severe.
