"So, So Dark..." Topic

I fear I have blundered. These newest figures have turned out way too dark. The dark blue and deep dark red I used have made for some very dark looking units. Then the wash I used made them even worse.

Can they be made a bit lighter? Highlights? How does one do such a thing?

Based on your preference – I would try

Dry Brushing on a lighter red or blue might work

or Dilute a lighter blue and a lighter red and paint over the areas

First, just try painting some of the basecoat colors over the main areas, trying to avoid the parts that are supposed to look dark. That will brighten the figure.

When that is done, you can consider highlighting.

I have had luck highlighting red with orange.

Highlights? How does one do such a thing?

The ideas mentioned above are all good. I'm just addressing this specific question of yours.

Dry-brushing is a specific technique. It's not difficult, but if you haven't done it before, try it out on something of no importance (like a ribbed plastic screw-top cap or something else with defined texture) until you get a feel for it.

As the name implies, you use a dry brush with as little paint as possible on it. Then you very lightly brush the end of the brush across the model. The objective is to transfer very small amounts of paint to the highest surfaces of the model.

Dry-brushing with a lighter tone of the base color (e.g., light blue dry-brush on darker blue basecoat) increases perceived depth, but it also lightens the model generally.

"Lighter tone" is usually achieved by mixing white into the base color. You can also get good effects by just using a lighter color. For example, a soldier in chain mail armor may get a flat black base coat and then be dry-brushed in silver to make the chain mail visible.