I thought your truck was a different year. White/blue is power. Then there are two from the negative side, green/yellow. The diagram is a little confusing, it shows two green/yellow off the coil for 87-88 and only one off the coil for 89. They made the splices different through the years apparently. So for the 89 the single green/yellow wire goes to an ignition suppression resistor, and the splice is off that. So from the ignition suppression resistor another green/yellow wire runs to the TFI module, spliced from the coil wire side. Now the ignition suppression resistor has a separate green/yellow wire that goes to the computer. Both 87 and 88 are spliced differently but with the same components.

I hope I explained that clearly enough. The coil is grounded through the bolts/bracket that attach it to the block.