This lexer will work nicely for apt show and apt-cache

syntax_files/apt.yaml

@@ -0,0 +1,44 @@
+filetype: apt
+
+detect: 
+    filename: "\\.apt"
+
+rules:
+    - constant.number: "(^[D|+].*)"
+    - preproc: "[0-9]+,?[0-9]*"
+    - preproc: "\\\\."
+    - preproc: "^(un.*)"
+    - constant: "^(ii.*)"
+    - comment: "^(rc.*)"
+    - type: "(i386|i486|i586|i686|amd64|\\<none\\>|athlon|ia64|alpha|alphaev5|alphaev56|alphapca56|alphaev6|alphaev67|sparc|sparcv9|sparc64armv3l|armv4b|armv4lm|ips|mipsel|ppc|iseries|ppcpseries|ppc64|m68k|m68kmint|Sgi|rs6000|i370|s390x|s390|noarch)"
+    - comment: "(^|[[:space:]])#([^{].*)?$"
+    - preproc: "[[:space:]]+$"
+    - indent-char: "	+ +| +	+"
+    - statement: "[[:space:]]([0-9~:.]{2,}[-+:.0-9a-z~]+)[[:space:]]"
+    - type: "(^| )!!(binary|bool|float|int|map|null|omap|seq|set|str) "
+    - constant:  "\\b(YES|yes|Y|y|ON|on|NO|no|N|n|OFF|off)\\b"
+    - constant: "\\b(true|false)\\b"
+    - statement: "(:[[:space:]]|\\[|\\]|:[[:space:]]+[|>]|^[[:space:]]*- )"
+    - identifier: "[[:space:]][\\*&][A-Za-z0-9]+"
+    - type: "[-.\\w]+:"
+    - statement: ":"
+    - special:  "(^---|^\\.\\.\\.|^%YAML|^%TAG)"
+
+    - constant.string:
+        start: "\""
+        end: "\""
+        skip: "\\\\."
+        rules:
+            - constant.specialChar: "\\\\."
+
+    - constant.string:
+        start: "'"
+        end: "'"
+        skip: "\\\\."
+        rules:
+            - constant.specialChar: "\\\\."
+
+    - comment:
+        start: "#"
+        end: "$"
+        rules: []