There are "warm" white LED's that you can buy. They have much more yellow and far less blue. In fact, you can often specify the colour temperature.

Unfortunately, most solar lights are quite cheap and have the bluish white LED's that you describe. In a lot of cases though, you could probably take apart the light and solder in the LED of your choice. And there are a *lot* of choices.

I make a lot of solar lanterns and similar solar/light art projects and I get all me LEDs from here: http://ledz.com/ An amazing selection. They have a distributer in the US, too.

Cheers, and good luck!
John Swanson