I have office phones that are connected to 4 lines. I want to add a cord-cordless 2 line phone. When I connect the new 2 line phone to the old jacks, I get no dial tone. Opening the jack I found 8 wires. Which colors do I connect to the standard 2 line jack of red/green and yellow/black? The 8 color wires are white-blue, blue, purple, red-white, orange, orange-white, green and white-green. I tried various combinations with no success. Thank you.

Start with a 4 conductor Line Cord(4 Pins for 2 lines)Connect your Red and Green (Line 1) and Yellow Black to your phone jack. Plug cordless phone into the dead jack,
Go to to where connections need to be made(your 4 conductors to existing 8).
Besides red/green being line 1 and yellow/black being line 2.
With twisted pair, white/blue/ blue/white is line 1, white/orange orange/white is line 2, white/green green/white is 3, and white brown/brown white is 4th pair. Sounds like from a larger bundle using additional.
I would try: white/blue to green, blue/white to red white orange to black and orange white to yellow.
Cordless phone will now work or not and you don't have to move by changing pairs,
If you have a cell phone, make a call to it to verify you are on the correct line.
Take note of the existing pairs, what colors are on existing red/green/yellow/black? Maintain thes pair and connect.
You can also call the line and don't answer and just look for ringing voltage.