Resistors have special code to change the colors, and bendable legs (which parts editor can’t currently deal with) so your best bet is to use the standard resistor in core parts and change the values in Inspector (otherwise you would need a separate part for each resistor value, modify the colors in the breadboard svg and remove the bendable legs, which isn’t particularly easy!)
No. In this case there are parts for each color in core parts but how Fritzing accesses them is via Inspector (it selects which part to use via the color parameter.) Again the easiest solution is to use inspector to change the colors. You can create custom parts for each color although as noted it isn’t that simple. This tutorial will tell you how to make a custom part.
I don’t remember if I covered how to remove bendable legs, perhaps not …
Peter