If it is the actual laser printer that displays the error message, then it is the printer itself that has ran out of memory - NOT the computer.
A laser printer has to store the whole page in memory before it can print the page, as it has to make an image that will be transferred to the drum in one pass.
Luckily you are using a laser printer that can be upgraded, see my site http:www.lasermemory.com for HP upgrades suitable for your printer.
You will be able to print full page photos if you add enough memory to the printer, but as you say, as its a mono printer, the will be mono (but the results are still pretty good)
Hope that helps.
lasermemory
August 2004