This is not true, I contacted AG asking the reason for the change and they told me specifically because they wanted to make her look different from ELizabeth.
<font size="2" face="Verdana, Helvetica, sans-serif">Someone here who was in the know, I think it was NellieGirl said they told her the change was to make Elizabeth different from Ruthie, who they think they will sell more of because Kit is far more popular than Felicity is.

This makes FAR more sense. If they'd wanted to make sure Felicity and Elizabeth looked different, it would have been easier to just change Felicity's hair color.

I think the line about changing her to look less like Felicity is just the line they give people to sound better.