I would not suggest steam cleaning canvas because it may shrink, and that would be bad. I'm not really sure but I wouldn't do it.
canvas
A tent or marquee-somewhere made of canvas where you can live.
Tent canvas.
In the United Kingdom, canvas tents can be purchased online from websites such as the Canvas Tent Shop, who are based in Bedford, Amazon or Ebay. The Soul Pad website also stocks them.
Will have to be custom made by a tent and awning shop.
A tent.
Made from canvas It is a General Purpose Tent or "G.P" for short
To effectively prevent and remove mildew from your tent, regularly clean and dry it thoroughly after each use. Use a mixture of water and vinegar or a specialized tent cleaner to remove mildew stains. Additionally, store your tent in a cool, dry place to prevent mildew growth.
Tent mold cleaner can be effective in removing mold from tents, but its effectiveness may vary depending on the severity of the mold and the specific product used. It is important to follow the instructions carefully and thoroughly clean the affected areas to ensure the best results.
To prevent and remove tent mold effectively, regularly clean and dry your tent after each use, store it in a cool, dry place, and use a mold-resistant spray or solution. If mold does appear, scrub it with a mixture of water and vinegar or a specialized mold cleaner, then thoroughly dry the tent before storing it.
Most canvas tents are older tents. If you have a newly manufactured tent that is made out of canvas then it may not be a high quality tent. Newer tents are made out of nylon and other man made materials. the colors are on the material before it is made. It sounds like your tent was dyed after the material was woven. The best thing I can tell you is to wash the tent and rinse it well. This may get out whatever colors that want to come out, out.
Mainly wood with iron fittings and parts. The tent/top was made of canvas.