Group Calendar Web Part Pop Up Color

We have created a branding theme for modern sharepoint sites to match corporate colors.  When clinking on a Group Calendar event, the pop up now applies a background color we didn't have in the theme as primary or secondary.  Just seems to be auto selected by SP.  It's too dark to read the text.  I've found the Them in the classic _catalog Theme Gallery and can pull the theme into NotePad to read it but can't seem to tell which variable controls the background of pop ups.  Just need it to be white (ffffff).  Anyone have a solution?

{"name":"(Company Theme Name)","isInverted":false,"palette":{"themeDarker":"#243360","themePrimary":"#17244C","themeSecondary":"#5e6d9b","themeTertiary":"#7885af","themeLight":"#94a0c2","themeLighter":"#b3bcd6","themeLighterAlt":"#d6dbea","black":"#000000","neutralDark":"#201f1e","neutralPrimary":"#323130","neutralPrimaryAlt":"#3b3a39","neutralSecondary":"#605e5c","neutralTertiary":"#a19f9d","neutralTertiaryAlt":"#c8c8c8","neutralLight":"#eaeaea","neutralLighter":"#f4f4f4","neutralLighterAlt":"#f8f8f8","white":"#ffffff","neutralQuaternaryAlt":"#dadada","neutralQuaternary":"#d0d0d0"},"displayMode":"light","secondaryColors":{"light":[{"themePrimary":"#ffffff","backgroundColor":"#17244C"},{"themePrimary":"#6BC289"},{"themePrimary":"#ffffff","backgroundColor":"#6BC289"},{"themePrimary":"#26A9E1"},{"themePrimary":"#ffffff","backgroundColor":"#26A9E1"},{"themePrimary":"#1B75BC"},{"themePrimary":"#ffffff","backgroundColor":"#1B75BC"},{"themePrimary":"#E7EBF6"},{"themePrimary":"#ffffff","backgroundColor":"#E7EBF6"},{"themePrimary":"#ACBFE3"},{"themePrimary":"#ffffff","backgroundColor":"#ACBFE3"},{"themePrimary":"#B6BBBF"},{"themePrimary":"#ffffff","backgroundColor":"#B6BBBF"}],"dark":[]}}