hi. im hand tracing a car. but i find myself having to keep inputting the stroke color i want. is there a way to lock a stroke color for the purpose of hand tracing?

Depends. If you want to lock it to the value you just used, you can switch that on in the preferences (Inkscape, not Document) in the menu for the tool you are using.
If you want to lock it to the color below (on the figure), you might want to try the calligraphy tool, which lets you alter properties of the line depending on the background you are currently tracing over.

Set the last path you drawer to the color you want and select that path, then double click the tool and hit take from selection. Just don't click on the color sample in the pop up menu. That will crash inkscape!

If I'm not mistaken, one can set the stroke width in the same manner.