diff --git a/book/source/17-zoom_certificates.md b/book/source/17-zoom_certificates.md
index ec928a0..1d1fd60 100644
--- a/book/source/17-zoom_certificates.md
+++ b/book/source/17-zoom_certificates.md
@@ -368,7 +368,7 @@ The signature is calculated from this hash digest.
 
 ```{figure} diag/direct_key_signature_packet.png
 :name: fig-direct-key-signature-packet
-:alt: Depicts a box with white background, title "Signature packet" and subtitle "Direct Key Signature (type ID 0x1F)". In the center a box with white background and green frame is shown. Inside it several items are listed, separated by green dotted horizontal lines. The first three are "Version", "Public-Key Algorithm" and "Hash Algorithm". The fourth item is called "Hashed area" and confines further sub-items by a light-green frame on the top and left side. The sub-items are "Signature Creation Time", "Key Expiration Time", "Preferred Symmetric Ciphers for v1 SEIPD", "Preferred Hash Algorithms", "Key Flags", "Features" and "Issuer Fingerprint". The fifth item is named "Unhashed area" and again introduces an area for sub-items, this time using a light-gray border on the top and left side. The unhashed area has no sub-items though. The last item is called "Cryptographic Signature", with the subtitle "by the primary key over primary key, subkey and signature metadata" and includes the green cryptographic signature symbol on the right side.
+:alt: Depicts a box with white background, title "Signature packet" and subtitle "Direct Key Signature (type ID 0x1F)". In the center a box with white background and yellow frame is shown. Inside it several items are listed, separated by yellow dotted horizontal lines. The first three are "Version", "Public-Key Algorithm" and "Hash Algorithm". The fourth item is called "Hashed area" and confines further sub-items by a light-yellow frame on the top and left side. The sub-items are "Signature Creation Time", "Key Expiration Time", "Preferred Symmetric Ciphers for v1 SEIPD", "Preferred Hash Algorithms", "Key Flags", "Features" and "Issuer Fingerprint". The fifth item is named "Unhashed area" and again introduces an area for sub-items, this time using a light-gray border on the top and left side. The unhashed area has no sub-items though. The last item is called "Cryptographic Signature", with the subtitle "by the primary key over primary key, subkey and signature metadata" and includes the green cryptographic signature symbol on the right side.
 
 Structure of a direct key signature packet.
 ```