My gum line is red at top of crown what problem could this be? Definitely a different color than rest of my gums. (photo)

There could be many things happening, perhaps all, perhaps just one, so it is important to find an experienced dentist or periodontist.  It could be:

Irregular/rough margin to crownBulky margin to crownExcess crown cement that didn't get removedMargin of crown too close to boneSpecific type of bacterial infection (periodontitis)Allergic reaction to the crown materialSince the answer isn't obvious, a clinical exam is needed.

the redness indicates inflammation and needs to be looked at by a dentist. If the crown has been on for more than 9 months, and is now red, it may be a related to the crown under the gumline. The gums can also react to cement, tartar buildup and bulky contour of the crown. 

Dear redness in your gum is due to the gingivitis cause by bacteria. In this case your gums become red, swollen and can bleed easily. So you should see dentist for the treatment and consultancy.

I agree with Dr. Schertzer about the possible things that can cause redness above a crown margin.  I would just add one more possibility to the list if nothing else can be found.  There is something called biologic  width.  It is a distance that the crown margin must be away from the bone forming the tooth socket under the gum.  It is approximately 3 mm.  on the front and back of the tooth and 4 mm. in between the teeth.  This is the measurement from the gum margin to the bone in a healthy gum where the space between the gum and the tooth (gingival sulcus) is about 1 mm. in depth.  If the crown is placed closer to the bone than that, in most cases, the gum will become chronically inflamed.  This is something else that should be considered when you see your dentist to evaluate the cause of your gum inflammation.

The redness is inflammation of the gum tissue.  Typically this is caused by something irritating the gums which can cause it to bleed easy, swell and get red.  The irritation maybe plaque/calculus buildup around the margin of the crown, excess cement, allergy or a rough crown margin.  I would see your dentist for evaluation.