I set the page link colors in a Transmogrified theme layer, and then tried to include them in the CSS by copying

a { $page_link_colors }
a:active { $page_link_active_colors }
a:hover { $page_link_hover_colors }
a:visited { $page_link_visited_colors }

from the layout layer, but it gave me an error.

Compile error: line 73, column 16: Unknown local variable $page_link_colors
S2::NodeVarRef, S2/NodeVarRef.pm, 180
S2::NodeVarRef, S2/NodeVarRef.pm, 151
S2::NodeTerm, S2/NodeTerm.pm, 174
S2::NodeTerm, S2/NodeTerm.pm, 66
S2::NodeSum, S2/NodeSum.pm, 65
S2::NodeSum, S2/NodeSum.pm, 64
S2::NodeSum, S2/NodeSum.pm, 64
S2::NodeSum, S2/NodeSum.pm, 64
S2::NodeSum, S2/NodeSum.pm, 64
S2::NodeSum, S2/NodeSum.pm, 64
S2::NodeSum, S2/NodeSum.pm, 64
S2::NodeSum, S2/NodeSum.pm, 64
S2::NodeTerm, S2/NodeTerm.pm, 76
S2::NodeTerm, S2/NodeTerm.pm, 66
S2::NodeExpr, S2/NodeExpr.pm, 46
S2::NodePrintStmt, S2/NodePrintStmt.pm, 55
S2::NodeStmtBlock, S2/NodeStmtBlock.pm, 108
S2::NodeFunction, S2/NodeFunction.pm, 230
S2::Checker, S2/Checker.pm, 374
S2::Compiler, S2/Compiler.pm, 34

, which was not what I was expecting based on this tutorial ...?

Also, it occurs to me that you didn't explain why some of the variables in your CSS example above had asterisks in them.