This is just cosmetic (a new spray), there is no difference in the effect.
From the Paladins wiki :
Gold Cards are special, cosmetic variants of regular cards that can be rolled from Radiant Chests. These golden cards will replace existing cards in the player's collection with an updated gold frame.
Once a Gold Card is acquired, the player will also receive a spray of that card's art. Gold Card sprays are usable only by the champion the card belongs to. Currently there are only a few Gold Cards with sprays. More Gold Card sprays will be added in the future.
You can select the special spray in the cosmetic tab of the champion.
To use the spray the default key is T, just use it near any wall :