If you ordered prior to the $2k increase, I am 99% sure that you will not incur the increase for changing your current order color.
I ordered prior to the $2k increase as well. In the timespan between then and just a week ago, I've changed from M3 RWD black interior, to white interior, back to black interior, and then to LR. Some of these changes occurred AFTER the $2k increase was announced, but my price for the full "menu" of model 3 options when I want to change something is still showing prices as of when I initially ordered it.
Explanation to me by SA is that if there are additional features announced in conjunction with price increase, then changing options for your current order will trigger the price increase. If it is pure price increase by Tesla without any added feature, then you get to retain the menu prices as of your original order date. Since this $2k increase seems to be purely market price adjustments without any features added, I got to keep my prices as of end of Feb when I initially ordered.
There is also a way to verify whether you would incur price changes prior to confirming your change. If you haven't completed the financing details in your tasks, there is a link on the right hand side of your order page to "edit order". Clicking that will allow you re-order your Model 3 with the options that you want. There you will be shown the prices that apply to you. You will see what you will be charged. If you like what you see, at the bottom of the page there will a button to confirm your changes, if not, there is another button to discard your changes. This way you can be sure what you will be charged when you change your order.
If you already completed the financing task, just text the online SA to "re-open" the financing options, and you will see the edit order button.
Hope this helps