It's a really good question and credit to you for having concerns about infringement of other artists work, on the other hand, unless your title goes AAA don't worry about it too much...
Basically if your character is obviously ripped from another game, the common thing to do would be mention this in your credits..ie, game by "Greaver", sprite copyright of "Somebody else".
This would show good faith in use of somebody else's work and cover you in most cases...
If your sprite is edited / recoloured it's usually fine to just declare this...If you have taken "inspiration" from elsewhere, saying your work is based on a certain work is usually acceptable, and the courteous thing to do...It all boils down to giving credit where due and not taking credit for other peoples work...
Ideas can't be copyrighted if you didn't stumble upon legends of mana, you would never know it was similar...keep it as it is.