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Clear skies doesn't always mean good seeing in fact sometimes the opposite. Good seeing requires steady air so look for little or no twinkling of the stars. When a could front passes the air is very clear but seeing is appalling.
You could try a good 2x Barlow with your 10mm eyepiece to get 180x which may be OK in exceptional seeing, but note the image brightness will be low. Image brightness is directly related to exit pupil which is the diameter of the cone of light entering your eye. Exit pupil = eyepiece focal length / telescope focal ratio.
In your case for a 10mm eyepiece, Magnification = 900/10=90, exit pupil = 10/12.86=0.78mm. The diameter of the cone of light entering your eye is 0.78mm (small). Add a 2x Barlow and this diameter is halved (0.39mm). An exit pupil of under 0.25mm is generally a little too small to see detail properly on any telescope.
A 2x Barlow doubles your telescope focal length or halves your eyepiece focal length.
Colour is visible especially on Saturn although the colours are subtle and Saturn is various shades of yellow. 150x is more than enough power for Saturn and Jupiter and yes, the planets are small in a telescope. A larger telescope at 150x will simply show you a brighter image which will make detail easier to spot.
Magnifications of between 120x and 240x are common for observing planets with telescopes from 60mm to 300mm. The larger telescopes will allow for brighter images at the higher powers but seeing will still be the limiting factor.
The 165x max limit for your telescope is not a hard and fast rule but generally only high quality apochromatic refractors can push these limits without the image breaking down although the image brighness will still be low for the smaller apertures.
Pushing the magnification past a practical limit gives a soft and fuzzy image with no extra detail being visible. It is often better to observe a smaller but sharper and brighter image.
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