Lighter? What do you mean? Do you mean it's tone?
Sorta, mainly the art style and the tone it sets. Shining in the Darkness, Shining Force and Landstalker were dark and kinda gothic in a good way. Shining Force two wasn't so far off, but was filled with lots of bad gaudy color choices. Shining Force III and Shing the Holy Ark were that bright colorful plastic kinda cgi, even the fmv. Golden Sun was more of the same and those PS2 Shining games don't look anything like the early titles, gameplay aside.
Ys III is such a different style of game, but Ys IV PCE already took the series to the limit of 'lighter-ness' before the games began to look like they could be from any number of other series. Eternal/Complete managed to balance the darker style with modern art, even though I'm still not happy with the appearance of that Adol.
I still like the style ys Seven uses (I loved Grandia) and it looks nice, but the art style is the only thing left to connect new games to the older ones since 2D rammin' gameplay is long gone.