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The -- does indicate a special order Paint color.
The two most popular 1970 Chevelle/Elco ZP3 colors were Daytona Yellow,and Monaco Orange,(Called Hugger Orange on the 69 Camaro).
Your Elco is Daytona Yellow now,but could have been a different color too.There were a host of other Special order paint colors Chevrolet would apply for the customer at extra cost.
To determine which color your Elco came with originaly,may be a Little difficult.
Look under the Vinyl top,if it has one,or behind the front fenders and quarters.Also look at the UnderBelly of your Elco to see if any over spray is Visible,and in the Bed area too,and in the Tail gate.If nothing shows,try pulling up some of the Window trim front and rear,to see if a color appears dfferent from what your Elco shows now.Pull up some of the carpet around the Door Jamb area too.Look at the metal floors.
If you Have a Flapper Door Cowl Hood,look at the Back top & Underneath of the Flapper door & inside the Hood to see if any overspray appears.
Also on your Buildsheet,the "xxxCustomer Order" is nothing unique,but look to the left of this to see if the factory stated an 8 digit Dupont paint code.
It will look like this:
926-99568
What is the Build date of Your Car on the Trim Tag?
Rick