The “.acb” file is actually an xml file. If you open the .acb file inside a text editor, you’ll see something like this:
<?xml version="1.0" encoding="UTF-8"?>
<colorBook>
<bookName>Eiffel Tower Screen-Shot-2021-03-10-at-8.25.35-AM copy</bookName>
<colorPage>
<pageColor>
<RGB8>
<red>245</red>
<green>244</green>
<blue>250</blue>
</RGB8>
</pageColor>
<colorEntry>
<RGB8>
<red>245</red>
<green>244</green>
<blue>250</blue>
</RGB8>
</colorEntry>
<colorEntry>
<RGB8>
<red>236</red>
<green>235</green>
<blue>237</blue>
</RGB8>
</colorEntry>
<colorEntry>
<RGB8>
<red>221</red>
<green>221</green>
<blue>224</blue>
</RGB8>
</colorEntry>
<colorEntry>
<RGB8>
<red>209</red>
<green>208</green>
<blue>210</blue>
</RGB8>
</colorEntry>
<colorEntry>
<RGB8>
<red>137</red>
<green>138</green>
<blue>145</blue>
</RGB8>
</colorEntry>
</colorPage>
</colorBook>
You’ll see the color values are stored in RGB format. We want them in hex.
Steps to convert acb to hexvalues
1. Convert your acb file to a tab-delimited file
1a. Create an xls file to convert your xml to a tab-delimited file.
Copy the following text into a text document, and name it with an .xsl ending. I used “xsl-pull_rgb_color.xsl”
<xsl:stylesheet version="2.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"/>
<xsl:template match="/">
<html>
<body>
<xsl:for-each select="colorBook/colorPage/colorEntry/RGB8">
<xsl:value-of select="red"/><xsl:text>	</xsl:text>
<xsl:value-of select="green"/><xsl:text>	</xsl:text>
<xsl:value-of select="blue"/>
<xsl:text>
</xsl:text>
</xsl:for-each>
</body>
</html>
</xsl:template>
</xsl:stylesheet>
1b. Open the .acb file in Xmplify.
1c. Go to Transform > Current Document, Using An XSL File as Template…

1d. Select the xsl file we just made: “xsl-pull_rgb_color.xsl”
1e. It will convert your acb file to this:
245 244 250
236 235 237
221 221 224
209 208 210
137 138 145
2. Copy the tab-delimited file into Google Sheets
Copy that text and paste it into a Google spreadsheet.
First column, red. Second column, blue. Third column, green.
3. Have Google Sheets make the conversion
Fourth column will be a formula: =dec2hex(A2)&dec2hex(B2)&dec2hex(C2)
The dec2hex function suggestion came from Craig Cornelius, Senior Software Engineer at Google

Boom. Now you have your hexvalues!
It’s a little clumsy. Maybe some day I’ll write something in PHP that simply converts the acb file to hex values in one step.