Can I print my e-Visa approval letter in black and white?

Yes, as long as it is legible to the Immigration Officer especially the QR Code. 

Most countries do not have specific requirements regarding the color of the printed e-Visa document. As long as the printed copy is clear and legible, it should be acceptable for presentation to immigration authorities.

However, it is always advisable to review the instructions provided by the e-Visa issuing authority or the official website of the country you are visiting. Some countries may have specific guidelines or requirements regarding the printing of e-Visa documents, so it's best to follow any instructions or recommendations provided.

If you are unsure about the printing requirements, you can consider printing a color copy to be on the safe side, especially if the e-Visa approval letter contains any color-coded information or security features that might be better visible in color.