Linterlux Bilgekoat Q's

[JWebber]

I have a quart of the interlux bilgekoat white, or some left over. I want to make it grey, as I understand the paint is a enamal, how can I tint it to gray? Can I just add some enamal black to it? Will this work or is a special type enamal paint? I'm using it to fill in some cracks that are cosmatic thru-out the bilge locker, front foot boards at helm and pasenger side. The existing is gray from factory.

Just want to match the existing and use up what I've got but its white. :facepalm: