There only seems to be resistor_220.svg and resistor_5bands.svg in the core/breadboard directory so I suspect Fritzing is using that as the base and modifying the colors in to a custom svg (which looks to be the case: when I drag a resistor in to breadboard, change it to 10 ohms then parts edit and save it to the mine parts bin and open the mine svg in Inkscape, the new color bands are in the svg). This indicates to me that we would likely need a code change to get this to work unfortunatly (unless of course @steelgoose has a magic fix, which he may ). Something that could convince it to do the change to an svg with .3 spacing should work if the color band change is generic enough, I’m just not sure how to convince core to use that alternate svg (or if that is possible without code changes).
(edit:) For the brave of heart this may be feasable. I just reduced the breadboard resistor_220.svg in core from .4 to .3 (doing in all resistors not just selected ones to .3) and the color bands still modify correctly, so it looks like it is looking for the color bands in the xml without caring about the spacing (good planning ). I’ll poke for a bit at making a new varient (I see that pcb is already done, there is a 300 mil varient it just doesn’t affect breadboard) and fixing up the bendable leads (which broke when I reduced, probably because I didn’t reduce the viewbox.) You will have to make changes to the core svg directory which github will overwrite at each new parts update but it may in fact work.