Thats a little Problem for all Cockpit Builders.
We need mostly 3,4,5, and 6 Digit Displays..... And all should have the same Color, font and size. You maby find a 3 Digit Displayblock in amber but a 4 Digit only in red..... Or You find a 4 Digit also in Amber but that is a little larger or include a Doublepoint between for a clock and looks bad.
Thats why a "perfect" cockpit is normaly designed with SingleDiggit Displays Only..... Here you choose a Display that have correct size, color and optic..... And you simply build blocks in size you need...... 4 Digit Display menas simply 4x1Diggit in a row.
The PROBLEM: A Single Digit have 9-10 Pins..... So a 4 Digit Display have up to 40 single wires that must be combined to finaly 12 Lines that end in your Max7219 Chip.
Thats verry hard to do with wires..... Here most user work with PCB´s .....
A good tactic is to buy ( or build yourself) PCB´s that have correct holes for your disply you choose..... And you have finaly a single PCB for every Combination ( 3,4,5,6 Digit e.g.)
You just solder your Digits or connect them to sockets ...... All wirework is done via lines on the PCB...... And finaly there is a output connector with for example 12 Lines for a 4 Digit Display...... Here you can connect your Max7219.
Looks like this.......
https://www.silicon-ark.co.uk/7-segment-5-digit-led-display-pcb
The absolutly perfect solution is to include the Displaysystem and also the Max7219 Chips directly on a complete PCB for the Element.... Then the Max Chips is also solder on the PCB and you have finaly just a 5 Pin Connector where you connect your 5 Lines to Mega ..... All other lines ( like chaining of MaxChips, Power managment , Lines from Max to Displays e.g.) are done on the PCB.
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Last Note about Color.
Some users simply work with WHITE Displays and use a visible collored foil on it..... Also a combination is possible..... A Yellow Diggit with a blue foil occure in a green Diplay
Maby you like to test this..... Usefull if you be able to order all needed Displays in White and your problem is only the color.
Looks normaly realistic, cause in real cockpit there is also a cover on the Displays..... Nobody cares about if this cover is blank or colored.