I tried to open your pic, but I need to log in using my Google account. Which I don't have. What am I missing here?
On Riplash's link, the color code is on page 4-2 and 4-3. You might try to follow a few of the colors and see if they are functionally uniform with what is in the manual. I think you will find that the colors in the manual match the wire colors on the boat.
Also, do the switches in Chapter 4 of the manual look like your switches?
Here's a link to the 1999 2700/2750 Regal user manual. You can look at it as a pdf and then print the whole thing or just the pages you need. Page 3-6 has a photos of the helm and the individual gauges. Again, page 4-2 and 4-3 are the wiring color codes. Page 4-4 has photos of the port and starboard switch banks. Odds are that these are the same as yours.
Chapter 12 is all the technical information any user might need some day, including electrical wiring schematic on page 12-8 and 12-9, helm systems on page 12-10. And there is much more. Best part about this site is that the manual as pdf can be downloaded as one manual. FREE! Check it out. https://s3.amazonaws.com/regalboats...00-2750-Owners-Manual-Final-6-3-2013.pdf