[lemorris]

Dup your color layer and try an image-adjust-hue/saturation

Check the colorize box and slide to your hearts content.

Another sweet spot is the image-adjust-variations and then of course you could dup your layer adjust the color on the copy and set the layer mode to overly, color, multiply whatever.

You can get the hue you want.

Nice drawing.

Can you give us a close up of the front wheel?

-Lemorris

p.s. image-adjust-selective color might get you there too. You can be specific to blues or reds or whatever.