@Beau Skunky  
Simplest solution? There’s no reason he can’t be a father and a mentor.

@Ferrotter  
I’m aware of that actually, but to be fair, Rarity & Sweetie are white-furred like their Dad. Not to mention the Cake baby twins are yellow like their Daddy Mr. Carrot Cake. (And the girl Pumpkin Cake has orange hair like him.) Not to mention Pinkie’s other sisters are greyish like their mother.
 
So there are a few exceptions, so it’s not like it’s “impossible” for ponies to have similar coloring/looks to their parents.
 
Still, I’d take some of things the cards say with gain of salt, as they have gotten a few things a bit off before.

@Beau Skunky  
Rarity’s mane is uniformly dark purple. Her sister’s is two-tone. Neither has their mother’s pink fur nor their father’s brown mane. No two ponies in the Pie family are the same color. Applejack is orange, her brother is red, her sister is yellow with a bright red mane, and her grandmother is green. The rest of her extended family trends towards earth tones but is all over the spectrum otherwise. Twilight shares no color or pattern with either of her parents, or her brother. Rumble is white with a black mane, while Thunderlane is dark grey with a blue and white mane, and they’re one of only two canonical pegasi families. Zipporwhill and Pegasus Dad have vaguely similar colors but hardly identical; she has a blonde mane while his is dark brown. Celestia is slightly pinkish off-white, while Luna is dark cornflower blue… and a Pinto!
 
Flitter and Cloudchaser have similar colors, but it’s not canon that they’re related to each other. (My headcanon is they are, but even if they are it’s practically the only time color similarity occurs in a familial relationship among the ponies.)
 
The cards are canon until contradicted by the show or comics. Yeah, I would have guessed it was Dash’s dad too, but it seems I would be been wrong.

@Ferrotter  
Eh, are you sure those are canon? They look to much alike to be anything other then father & daughter to me, so it seems like a cop-out if they’re changing him to a “mentor.”

@Killbeat
 
@Beau Skunky  
The cards identify that pony as her mentor Rainbow Blaze, not her father or “Rainbow Dad.”
 

@Killbeat  
Yeeeaaaah, Rainbow Dad looks to much like her.

Three Words: Rainbow Dash’s dad.