Reliable TTL ( Transistor Transistor Logic ) technology which is guaranteed to work after more than 10 years, 20 years and even 30 years.
Description and schema's how to built in link attached.

A bit of soldering and discipline is required here, but as long as good procedures are followed the end result is great.
The clock can be built to your own idea regarding the displays and what color is required for the led's.

For a 8 digit clock, materials required are :
TTL IC's
7447 x 8
7490 x 10
7400 x 2
7413 x 1
BC547 x 10
7 segment displays x 8

Then parts from the junk box as below:

resistors, vero board, 5 Volts 7805 regulator
Capacitors, Tantalums, lots of jumper wires 1N4007
15VA transformer.

Good reference reading are the following books:
TTL Cookbook from Don Lancaster (USA)
Digitale klokschakelingen van Herbert Bernstein (NL)
van Flip flop to digitale klok van Horst Pelka (NL)

http://www.electro-tech-online.com/electronic-projects-design-ideas-reviews/25628-ttl-clock-7447-7490-7400-ics-6.html#post855407