Reddit mentions of Timbermate White Hardwood Wood Filler 8oz Jar

You can sand back down to the bare wood again and start over, but it'll be a little work. Couple notes though:

• You can only stain/dye things to be darker than they already are. If your filler is already too dark, you need to buy lighter filler.
  
  
• If you want to make the wood darker than the filler, then you have to stain/dye the guitar before applying the filler... otherwise you'll just stain/dye the filler at the same time as you're coloring the rest of the guitar. Applying filler before color only works if you want the filler darker than the wood. Also, the color in the filler will color the rest of your wood if you haven't already sealed it.
  
  
• I have never dyed my own filler. My advice would be to spend $15 on the right wood filler (something like https://www.amazon.com/Timbermate-White-Hardwood-Wood-Filler/dp/B001NV4VG4 ) and $10 on a 15mL sample bottle of dye (such as http://www.woodessence.com/ColorFX-Dye-Individual-Bottles-P46C12.aspx ), which is more dye than you'll ever need for one guitar. It's always easier to use the right materials instead of trying to force the wrong materials to do something they were never meant to do.