Swashbuckler have Swashbuckler Finesse as a character feature.
Type: Swashbuckler Class Feature
Description: _A swashbuckler gains the benefits of the Weapon Finesse feat with light or one-handed piercing melee weapons, and she can use her Charisma score in place of Intelligence as a prerequisite for combat feats. This ability counts as having the Weapon Finesse feat for purposes of meeting feat prerequisites. _
Source: Paizo Inc. - Advanced Class Guide, p.56
With this, a Swashbuckler character could obtain the Slashing Grace feat.
The Slashing Grace feat appears as Red, as if the character doesn't have Weapon Finesse... and even by adding Weapon Finesse as a feat the Slashing Grace can't be added.