It is not uncommon for succulents to turn pale colors when growing. But given they have been in a north window. The cactus needs a south window, east or west if that's not available, and the Haworthia needs east or west or a shaded south exposure.

Quite a bit more light needed. Consider grow light, windowsill is not enough, and 'next to N window' is barely enough....

Assuming your are in the northern hemisphere, yes a north window won't provide nearly enough sunlight. If you are in a place like Australia then the north window would be the best source of sunlight. Based on how your plants look I'd guess you are in the northern hemisphere. Additionally, this time of the year, winter, in the northern hemisphere you might have a lot of cloudy days. I've found that a few of my plants in a south facing window still don't get enough sunlight to keep them healthy through the winter. You might need a grow light for the cactus. The Haworthia would probably be OK just with a south facing window right now and you might want to put it someplace that gets a bit less light during the summer months if the eaves of your roof don't shade the window on the south side. Haworthia usually aren't plans that like full sunlight.

If you only have a north window, buy a grow light to place by the window with the plants. It does not need to be fancy. It should be full spectrum with white light, not blue, red or purple, but white or yellow light. Simple Desktop Grow Light

Great tip