I remember repas by connecting it with the English word "repast", meaning meal. Let's go have a light repast.
Regular adjectives are placed after the noun.
Some of them, still, can be placed before the noun to give it a more subjective meaning.
"un repas léger" is a light meal, with not too big portions, not too many calories, etc.
"un léger repas" can be used for a stylistic effect either as an understatement (actually, the meal was so light it was hardly a meal) or an antiphrase (actually, the meal was really heavy).
Thanks, sitesurf. I had not encountered this use of léger as an antiphrase before. Can we use other adjectives in this way to create an antiphrase or a sarcastic remark? Could you remark, of an ugly man , for example, "C'est un bel homme, lui"? Or of a tramp, "C'est un bien habillé, lui"?